Sync with tzcode2024a:
Release 2024a - 2024-02-01 09:28:56 -0800

Changes to code

The FROM and TO columns of Rule lines can no longer be "minimum"
or an abbreviation of "minimum", because TZif files do not support
DST rules that extend into the indefinite past - although these
rules were supported when TZif files had only 32-bit data, this
stopped working when 64-bit TZif files were introduced in 1995.
This should not be a problem for realistic data, since DST was
first used in the 20th century. As a transition aid, FROM columns
like "minimum" are now diagnosed and then treated as if they were
the year 1900; this should suffice for TZif files on old systems
with only 32-bit time_t, and it is more compatible with bugs in
2023c-and-earlier localtime.c. (Problem reported by Yoshito
Umaoka.)

localtime and related functions no longer mishandle some
timestamps that occur about 400 years after a switch to a time
zone with a DST schedule. In 2023d data this problem was visible
for some timestamps in November 2422, November 2822, etc. in
America/Ciudad_Juarez. (Problem reported by Gilmore Davidson.)

strftime %s now uses tm_gmtoff if available. (Problem and draft
patch reported by Dag-Erling Sm��rgrav.)

Changes to build procedure

The leap-seconds.list file is now copied from the IERS instead of
from its downstream counterpart at NIST, as the IERS version is
now in the public domain too and tends to be more up-to-date.
(Thanks to Martin Burnicki for liaisoning with the IERS.)

Changes to documentation

The strftime man page documents which struct tm members affect
which conversion specs, and that tzset is called. (Problems
reported by Robert Elz and Steve Summit.)

Fix yet another wording (editing) botch noticed by uwe@

zic(8): missed a .Ql

Fix a wording botch noticed by uwe@ (and one more smaller one), and
a few more markup issues. While here, consistemntly use minus when
minus is meant, rather that just using a hyphen.

zic(8): more markup fixes

Still need to go over the tables.

More markup fixes. This man page remains exceedingly ugly (particularly
relating to vertical space - which often is missing where it would be
better if it weren't, or is present and wasteful/ugly).

PR/57757: Izumi Tsutsui: Fix markup errors

Update tzcode from 2022g to 2023c:

Release 2023c - 2023-03-28 12:42:14 -0700

Release 2023b - 2023-03-23 19:50:38 -0700

Release 2023a - 2023-03-22 12:39:33 -0700

Changes to code

You can now tell tzselect local time, to simplify later choices.
Select the 'time' option in its first prompt.

You can now compile with -DTZNAME_MAXIMUM=N to limit time zone
abbreviations to N bytes (default 255). The reference runtime
library now rejects POSIX-style TZ strings that contain longer
abbreviations, treating them as UTC. Previously the limit was
platform dependent and abbreviations were silently truncated to
16 bytes even when the limit was greater than 16.

The code by default is now designed for C99 or later. To build in
a C89 environment, compile with -DPORT_TO_C89. To support C89
callers of the tzcode library, compile with -DSUPPORT_C89. The
two new macros are transitional aids planned to be removed in a
future version, when C99 or later will be required.

The code now builds again on pre-C99 platforms, if you compile
with -DPORT_TO_C89. This fixes a bug introduced in 2022f.

On C23-compatible platforms tzcode no longer uses syntax like
'static [[noreturn]] void usage(void);'. Instead, it uses
'[[noreturn]] static void usage(void);' as strict C23 requires.
(Problem reported by Houge Langley.)

The code's functions now constrain their arguments with the C
'restrict' keyword consistently with their documentation.
This may allow future optimizations.

zdump again builds standalone with ckdadd and without setenv,
fixing a bug introduced in 2022g. (Problem reported by panic.)

leapseconds.awk can now process a leap seconds file that never
expires; this might be useful if leap seconds are discontinued.

Changes to commentary

tz-link.html has a new section "Coordinating with governments and
distributors". (Thanks to Neil Fuller for some of the text.)

To improve tzselect diagnostics, zone1970.tab's comments column is
now limited to countries that have multiple timezones.

Note that leap seconds are planned to be discontinued by 2035.

Fix formatting corruption for manpages from tzcode.

Comment out .TH macros, that cause mandoc(1) to run into man(7) mode.

branches: 1.41.2;
Merge in 2022g:

Although tzcode still works with C89, bugs found in recent routine
maintenance indicate that bitrot has set in and that in practice
C89 is no longer used to build tzcode. As it is a maintenance
burden, support for C89 is planned to be removed soon. Instead,
please use compilers compatible with C99, C11, C17, or C23.

timegm, which tzcode implemented in 1989, will finally be
standardized 34 years later as part of C23, so timegm is now
supported even if STD_INSPIRED is not defined.

Fix bug in zdump's tzalloc emulation on hosts that lack tm_zone.
(Problem reported by ��o��n Tr���n C��ng Danh.)

Fix bug in zic on hosts where malloc(0) yields NULL on success.
(Problem reported by Tim McBrayer for AIX 6.1.)

Fix zic configuration to avoid linkage failures on some platforms.
(Problems reported by Gilmore Davidson and Igor Ivanov.)

Work around MS-Windows nmake incompatibility with POSIX.
(Problem reported by Manuela Friedrich.)

Port mktime and strftime to debugging platforms where accessing
uninitialized data has undefined behavior (strftime problem
reported by Robert Elz).

Check more carefully for unlikely integer overflows, preferring
C23 <stdckdint.h> to overflow checking by hand, as the latter has
had obscure bugs.

Update to tzcode2022f

Changes to code

zic now supports links to links regardless of input line order.
For example, if Australia/Sydney is a Zone, the lines
Link Australia/Canberra Australia/ACT
Link Australia/Sydney Australia/Canberra
now work correctly, even though the shell commands
ln Australia/Canberra Australia/ACT
ln Australia/Sydney Australia/Canberra
would fail because the first command attempts to use a link
Australia/Canberra that does not exist until after the second
command is executed. Previously, zic had unspecified behavior if
a Link line's target was another link, and zic often misbehaved if
a Link line's target was a later Link line.

Fix line number in zic's diagnostic for a link to a link.

Fix a bug that caused localtime to mishandle timestamps starting
in the year 2438 when reading data generated by 'zic -b fat' when
distant-future DST transitions occur at times given in standard
time or in UT, not the usual case of local time. This occurs when
the corresponding .zi Rule lines specify DST transitions with TO
columns of 'max' and AT columns that end in 's' or 'u'. The
number 2438 comes from the 32-bit limit in the year 2038, plus the
400-year Gregorian cycle. (Problem reported by Bradley White.)

On glibc 2.34 and later, which optionally supports 64-bit time_t
on platforms like x86 where time_t was traditionally 32 bits,
default time_t to 64 instead of 32 bits. This lets functions like
localtime support timestamps after the year 2038, and fixes
year-2038 problems in zic when accessing files dated after 2038.
To continue to limit time_t to 32 bits on these platforms, use
"make CFLAGS='-D_TIME_BITS=32'".

In C code, do not enable large-file support on platforms like AIX
and macOS that no longer need it now that tzcode does not use
off_t or related functions like 'stat'. Large-file support is
still enabled by default on GNU/Linux, as it is needed for 64-bit
time_t support.

In C code, prefer C23 keywords to pre-C23 macros for alignof,
bool, false, and true. Also, use the following C23 features if
available: __has_include, unreachable.

zic no longer works around Qt bug 53071, as the relevant Qt
releases have been out of support since 2019. This change affects
only fat TZif files, as thin files never had the workaround.

zdump no longer modifies the environ vector when compiled on
platforms lacking tm_zone or when compiled with -DUSE_LTZ=0.
This avoid undefined behavior on POSIX platforms.

add missing text.

Welcome to 2022b:

zic has a new option '-R @N' to output explicit transitions < N.
(Need suggested by Almaz Mingaleev.)

'zic -r @N' no longer outputs bad data when N < first transition.
(Problem introduced in 2021d and reported by Peter Krefting.)

zic now checks its input for NUL bytes and unterminated lines, and
now supports input line lengths up to 2048 (not 512) bytes.

gmtime and related code now use the abbreviation "UTC" not "GMT".
POSIX is being revised to require this.

When tzset and related functions set vestigial static variables
like tzname, they now prefer specified timestamps to unspecified ones.
(Problem reported by Almaz Mingaleev.)

zic no longer complains "can't determine time zone abbreviation to
use just after until time" when a transition to a new standard
time occurs simultanously with the first DST fallback transition.

Change to code and documentation from 2021a -> 2021e

Release 2021e - 2021-10-21 18:41:00 -0700

Changes to code

none


Release 2021d - 2021-10-15 13:48:18 -0700

Changes to code

'zic -r' now uses "-00" time zone abbreviations for intervals
with UT offsets that are unspecified due to -r truncation.
This implements a change in draft Internet RFC 8536bis.


Release 2021c - 2021-10-01 14:21:49 -0700

Changes to code

Fix a bug in 'zic -b fat' that caused old timestamps to be
mishandled in 32-bit-only readers (problem reported by Daniel
Fischer).

Changes to documentation

Distribute the SECURITY file (problem reported by Andreas Radke).


Release 2021b - 2021-09-24 16:23:00 -0700

Changes to maintenance procedure

The new file SECURITY covers how to report security-related bugs.

Several backward-compatibility links have been moved to the
'backward' file. These links, which range from Africa/Addis_Ababa
to Pacific/Saipan, are only for compatibility with now-obsolete
guidelines suggesting an entry for every ISO 3166 code.
The intercontinental convenience links Asia/Istanbul and
Europe/Nicosia have also been moved to 'backward'.

Changes to code

zic now creates each output file or link atomically,
possibly by creating a temporary file and then renaming it.
This avoids races where a TZ setting would temporarily stop
working while zic was installing a replacement file or link.

zic -L no longer omits the POSIX TZ string in its output.
Starting with 2020a, zic -L truncated its output according to the
"Expires" directive or "#expires" comment in the leapseconds file.
The resulting TZif files omitted daylight saving transitions after
the leap second table expired, which led to far less-accurate
predictions of times after the expiry. Although future timestamps
cannot be converted accurately in the presence of leap seconds, it
is more accurate to convert near-future timestamps with a few
seconds error than with an hour error, so zic -L no longer
truncates output in this way.

Instead, when zic -L is given the "Expires" directive, it now
outputs the expiration by appending a no-change entry to the leap
second table. Although this should work well with most TZif
readers, it does not conform to Internet RFC 8536 and some pickier
clients (including tzdb 2017c through 2021a) reject it, so
"Expires" directives are currently disabled by default. To enable
them, set the EXPIRES_LINE Makefile variable. If a TZif file uses
this new feature it is marked with a new TZif version number 4,
a format intended to be documented in a successor to RFC 8536.

zic -L LEAPFILE -r @LO no longer generates an invalid TZif file
that omits leap second information for the range LO..B when LO
falls between two leap seconds A and B. Instead, it generates a
TZif version 4 file that represents the previously-missing
information.

The TZif reader now allows the leap second table to begin with a
correction other than -1 or +1, and to contain adjacent
transitions with equal corrections. This supports TZif version 4.

The TZif reader now lets leap seconds occur less than 28 days
apart. This supports possible future TZif extensions.

Fix bug that caused 'localtime' etc. to crash when TZ was
set to a all-year DST string like "EST5EDT4,0/0,J365/25" that does
not conform to POSIX but does conform to Internet RFC 8536.

Fix another bug that caused 'localtime' etc. to crash when TZ was
set to a POSIX-conforming but unusual TZ string like
"EST5EDT4,0/0,J365/0", where almost all the year is DST.

Fix yet another bug that caused 'localtime' etc. to mishandle slim
TZif files containing leap seconds after the last explicit
transition in the table, or when handling far-future timestamps
in slim TZif files lacking leap seconds.

Fix localtime misbehavior involving positive leap seconds.
This change affects only behavior for "right" system time,
which contains leap seconds, and only if the UT offset is
not a multiple of 60 seconds when a positive leap second occurs.
(No such timezone exists in tzdb, luckily.) Without the fix,
the timestamp was ambiguous during a positive leap second.
With the fix, any seconds occurring after a positive leap second
and within the same localtime minute are counted through 60, not
through 59; their UT offset (tm_gmtoff) is the same as before.
Here is how the fix affects timestamps in a timezone with UT
offset +01:23:45 (5025 seconds) and with a positive leap second at
1972-06-30 23:59:60 UTC (78796800):

time_t without the fix with the fix
78796800 1972-07-01 01:23:45 1972-07-01 01:23:45 (leap second)
78796801 1972-07-01 01:23:45 1972-07-01 01:23:46
...
78796815 1972-07-01 01:23:59 1972-07-01 01:23:60
78796816 1972-07-01 01:24:00 1972-07-01 01:24:00

Fix an unlikely bug that caused 'localtime' etc. to misbehave if
civil time changes a few seconds before time_t wraps around, when
leap seconds are enabled.

Fix bug in zic -r; in some cases, the dummy time type after the
last time transition disagreed with the TZ string, contrary to
Internet RFC 8563 section 3.3.

Fix a bug with 'zic -r @X' when X is a negative leap second that
has a nonnegative correction. Without the fix, the output file
was truncated so that X appeared to be a positive leap second.
Fix a similar, even-less-likely bug when truncating at a positive
leap second that has a nonpositive correction.

zic -r now reports an error if given rolling leap seconds, as this
usage has never generally worked and is evidently unused.

zic now generates a POSIX-conforming TZ string for TZif files
where all-year DST is predicted for the indefinite future.
For example, for all-year Eastern Daylight Time, zic now generates
"XXX3EDT4,0/0,J365/23" where it previously generated
"EST5EDT,0/0,J365/25" or "". (Thanks to Michael Deckers for
noting the possibility of POSIX conformance.)

zic.c no longer requires sys/wait.h (thanks to spazmodius for
noting it wasn't needed).

When reading slim TZif files, zdump no longer mishandles leap
seconds on the rare platforms where time_t counts leap seconds,
fixing a bug introduced in 2014g.

zdump -v now outputs timestamps at boundaries of what localtime
and gmtime can represent, instead of the less-useful timestamps
one day after the minimum and one day before the maximum.
(Thanks to Arthur David Olson for prototype code, and to Manuela
Friedrich for debugging help.)

zdump's -c and -t options are now consistently inclusive for the
lower time bound and exclusive for the upper. Formerly they were
inconsistent. (Confusion noted by Martin Burnicki.)

Changes to build procedure

You can now compile with -DHAVE_MALLOC_ERRNO=0 to port to
non-POSIX hosts where malloc doesn't set errno.
(Problem reported by Jan Engelhardt.)

Changes to documentation

tzfile.5 better matches a draft successor to RFC 8536
<https://datatracker.ietf.org/doc/draft-murchison-rfc8536bis/01/>.

Merge tzcode-2021a
- No comments in the changelog about the code changes.

Merge tzcode2020b (except we keep tzsetwall(3) for now for compatibility,
and we were "slim" already)

Support for zic's long-obsolete '-y YEARISTYPE' option has been
removed and, with it, so has support for the TYPE field in Rule
lines, which is now reserved for compatibility with earlier zic.
These features were previously deprecated in release 2015f.
(Thanks to Tim Parenti.)

zic now defaults to '-b slim' instead of to '-b fat'.

zic's new '-l -' and '-p -' options uninstall any existing
localtime and posixrules files, respectively.

The undocumented and ineffective tzsetwall function has been
removed.

Bring in 2020a

Sync with 2019b:

zic's new -b option supports a way to control data bloat and to
test for year-2038 bugs in software that reads TZif files.
'zic -b fat' and 'zic -b slim' generate larger and smaller output;
for example, changing from fat to slim shrinks the Europe/London
file from 3648 to 1599 bytes, saving about 56%. Fat and slim
files represent the same set of timestamps and use the same TZif
format as documented in tzfile(5) and in Internet RFC 8536.
Fat format attempts to work around bugs or incompatibilities in
older software, notably software that mishandles 64-bit TZif data
or uses obsolete TZ strings like "EET-2EEST" that lack DST rules.
Slim format is more efficient and does not work around 64-bit bugs
or obsolete TZ strings. Currently zic defaults to fat format
unless you compile with -DZIC_BLOAT_DEFAULT=\"slim\"; this
out-of-the-box default is intended to change in future releases
as the buggy software often mishandles timestamps anyway.

zic no longer treats a set of rules ending in 2037 specially.
Previously, zic assumed that such a ruleset meant that future
timestamps could not be predicted, and therefore omitted a
POSIX-like TZ string in the TZif output. The old behavior is no
longer needed for current tzdata, and caused problems with newlib
when used with older tzdata (reported by David Gauchard).

zic no longer generates some artifact transitions. For example,
Europe/London no longer has a no-op transition in January 1996.

merge 2019a

Changes to code

zic now has an -r option to limit the time range of output data.
For example, 'zic -r @1000000000' limits the output data to
timestamps starting 1000000000 seconds after the Epoch.
This helps shrink output size and can be useful for applications
not needing the full timestamp history, such as TZDIST truncation;
see Internet RFC 8536 section 5.1. (Inspired by a feature request
from Christopher Wong, helped along by bug reports from Wong and
from Tim Parenti.)

Changes to documentation

Mention Internet RFC 8536 (February 2019), which documents TZif.

tz-link.html now cites tzdata-meta
<https://tzdata-meta.timtimeonline.com/>.

Welcome tzcode-2018g

Changes to code

When generating TZif files with leap seconds, zic no longer uses a
format that trips up older 32-bit clients, fixing a bug introduced
in 2018f. (Reported by Daniel Fischer.) Also, the zic workaround
for QTBUG-53071 now also works for TZif files with leap seconds.

The translator to rearguard format now rewrites the line
"Rule Japan 1948 1951 - Sep Sat>=8 25:00 0 S" to
"Rule Japan 1948 1951 - Sep Sun>=9 1:00 0 S".
This caters to zic before 2007 and to Oracle TZUpdater 2.2.0
and earlier. (Reported by Christos Zoulas.)

Changes to documentation

tzfile.5 has new sections on interoperability issues.

Update to 2018f:

Changes to code

zic now always generates TZif files where time type 0 is used for
timestamps before the first transition. This simplifies the
reading of TZif files and should not affect behavior of existing
TZif readers because the same set of time types is used; only
their internal indexes may have changed. This affects only the
legacy zones EST5EDT, CST6CDT, MST7MDT, PST8PDT, CET, MET, and
EET, which previously used nonzero types for these timestamps.

Because of the type 0 change, zic no longer outputs a dummy
transition at time -2**59 (before the Big Bang), as clients should
no longer need this to handle historical timestamps correctly.
This reverts a change introduced in 2013d and shrinks most TZif
files by a few bytes.

zic now supports negative time-of-day in Rule and Leap lines, e.g.,
"Rule X min max - Apr lastSun -6:00 1:00 -" means the transition
occurs at 18:00 on the Saturday before the last Sunday in April.
This behavior was documented in 2018a but the code did not
entirely match the documentation.

localtime.c no longer requires at least one time type in TZif
files that lack transitions or have a POSIX-style TZ string. This
future-proofs the code against possible future extensions to the
format that would allow TZif files with POSIX-style TZ strings and
without transitions or time types.

A read-access subscript error in localtime.c has been fixed.
It could occur only in TZif files with timecnt == 0, something that
does not happen in practice now but could happen in future versions.

localtime.c no longer ignores TZif POSIX-style TZ strings that
specify only standard time. Instead, these TZ strings now
override the default time type for timestamps after the last
transition (or for all time stamps if there are no transitions),
just as DST strings specifying DST have always done.

leapseconds.awk now outputs "#updated" and "#expires" comments,
and supports leap seconds at the ends of months other than June
and December. (Inspired by suggestions from Chris Woodbury.)

Changes to documentation

New restrictions: A Rule name must start with a character that
is neither an ASCII digit nor "-" nor "+", and an unquoted name
should not use characters in the set "!$%&'()*,/:;<=>?@[\]^`{|}~".
The latter restriction makes room for future extensions (a
possibility noted by Tom Lane).

tzfile.5 now documents what time types apply before the first and
after the last transition, if any.

Documentation now uses the spelling "timezone" for a TZ setting
that determines timestamp history, and "time zone" for a
geographic region currently sharing the same standard time.

The name "TZif" is now used for the tz binary data format.

tz-link.htm now mentions the A0 TimeZone Migration utilities.
(Thanks to Aldrin Martoq for the link.)

branches: 1.29.2;
Merge 2018e

Changes to code

zic now accepts subsecond precision in expressions like
00:19:32.13, which is approximately the legal time of the
Netherlands from 1835 to 1937. However, because it is
questionable whether the few recorded uses of non-integer offsets
had subsecond precision in practice, there are no plans for tzdata
to use this feature. (Thanks to Steve Allen for pointing out
the limitations of historical data in this area.)

The code is a bit more portable to MS-Windows. Installers can
compile with -DRESERVE_STD_EXT_IDS on MS-Windows platforms that
reserve identifiers like 'localtime'. (Thanks to Manuela
Friedrich).

Changes to documentation and commentary

theory.html now outlines tzdb's extensions to POSIX's model for
civil time, and has a section "POSIX features no longer needed"
that lists POSIX API components that are now vestigial.
(From suggestions by Steve Summit.) It also better distinguishes
time zones from tz regions. (From a suggestion by Guy Harris.)

Commentary is now more consistent about using the phrase "daylight
saving time", to match the C name tm_isdst. Daylight saving time
need not occur in summer, and need not have a positive offset from
standard time.

Commentary about historical transitions in Uruguay has been expanded
with links to many relevant legal documents.
(Thanks to Tim Parenti.)

Commentary now uses some non-ASCII characters with Unicode value
less than U+0100, as they can be useful and should work even with
older editors such as XEmacs.

branches: 1.28.2;
Merge tzcode2018c [ changelog with changes to tzdata sections removed ]

Release 2018c - 2018-01-22 23:00:44 -0800

Changes to build procedure

The build procedure now works around mawk 1.3.3's lack of support
for character class expressions. (Problem reported by Ohyama.)


Release 2018b - 2018-01-17 23:24:48 -0800

Changes to build procedure

The distribution now contains the file 'pacificnew' again.
This file was inadvertantly omitted in the 2018a distribution.
(Problem reported by Matias Fonzo.)


Release 2018a - 2018-01-12 22:29:21 -0800

Changes to build procedure

The default installation locations have been changed to mostly
match Debian circa 2017, instead of being designed as an add-on to
4.3BSD circa 1986. This affects the Makefile macros TOPDIR,
TZDIR, MANDIR, and LIBDIR. New Makefile macros TZDEFAULT, USRDIR,
USRSHAREDIR, BINDIR, ZDUMPDIR, and ZICDIR let installers tailor
locations more precisely. (This responds to suggestions from
Brian Inglis and from Steve Summit.)

The default installation procedure no longer creates the
backward-compatibility link US/Pacific-New, which causes
confusion during user setup (e.g., see Debian bug 815200).
Use 'make BACKWARD="backward pacificnew"' to create the link
anyway, for now. Eventually we plan to remove the link entirely.

tzdata.zi now contains a version-number comment.
(Suggested by Tom Lane.)

The Makefile now quotes values like BACKWARD more carefully when
passing them to the shell. (Problem reported by Zefram.)

Builders no longer need to specify -DHAVE_SNPRINTF on platforms
that have snprintf and use pre-C99 compilers. (Problem reported
by Jon Skeet.)

Changes to code

zic has a new option -t FILE that specifies the location of the
file that determines local time when TZ is unset. The default for
this location can be configured via the new TZDEFAULT makefile
macro, which defaults to /etc/localtime.

Diagnostics and commentary now distinguish UT from UTC more
carefully; see theory.html for more information about UT vs UTC.

zic has been ported to GCC 8's -Wstringop-truncation option.
(Problem reported by Martin Sebor.)

Changes to documentation and commentary

The zic man page now documents the longstanding behavior that
times and years can be out of the usual range, with negative times
counting backwards from midnight and with year 0 preceding year 1.
(Problem reported by Michael Deckers.)

The theory.html file now mentions the POSIX limit of six chars
per abbreviation, and lists alphabetic abbreviations used.

The files tz-art.htm and tz-link.htm have been renamed to
tz-art.html and tz-link.html, respectively, for consistency with
other file names and to simplify web server configuration.

Welcome to 2017c:

zic and the reference runtime now reject multiple leap seconds
within 28 days of each other, or leap seconds before the Epoch.
As a result, support for double leap seconds, which was
obsolescent and undocumented, has been removed. Double leap
seconds were an error in the C89 standard; they have never existed
in civil timekeeping. (Thanks to Robert Elz and Bradley White for
noticing glitches in the code that uncovered this problem.)

zic now warns about use of the obsolescent and undocumented -y
option, and about use of the obsolescent TYPE field of Rule lines.

zic now allows unambiguous abbreviations like "Sa" and "Su" for
weekdays; formerly it rejected them due to a bug. Conversely, zic
no longer considers non-prefixes to be abbreviations; for example,
it no longer accepts "lF" as an abbreviation for "lastFriday".
Also, zic warns about the undocumented usage with a "last-"
prefix, e.g., "last-Fri".

Similarly, zic now accepts the unambiguous abbreviation "L" for
"Link" in ordinary context and for "Leap" in leap-second context.
Conversely, zic no longer accepts non-prefixes such as "La" as
abbreviations for words like "Leap".

zic no longer accepts leap second lines in ordinary input, or
ordinary lines in leap second input. Formerly, zic sometimes
warned about this undocumented usage and handled it incorrectly.

The new macro HAVE_TZNAME governs whether the tzname external
variable is exported, instead of USG_COMPAT. USG_COMPAT now
governs only the external variables "timezone" and "daylight".
This change is needed because the three variables are not in the
same category: although POSIX requires tzname, it specifies the
other two variables as optional. Also, USG_COMPAT is now 1 or 0:
if not defined, the code attempts to guess it from other macros.

localtime.c and difftime.c no longer require stdio.h, and .c files
other than zic.c no longer require sys/wait.h.

zdump.c no longer assumes snprintf. (Reported by Jonathan Leffler.)

Calculation of time_t extrema works around a bug in GCC 4.8.4
(Reported by Stan Shebs and Joseph Myers.)

zic.c no longer mistranslates formats of line numbers in non-English
locales. (Problem reported by Benno Schulenberg.)

Several minor changes have been made to the code to make it a
bit easier to port to MS-Windows and Solaris. (Thanks to Kees
Dekker for reporting the problems.)

Changes to documentation and commentary

The two new files 'theory.html' and 'calendars' contain the
contents of the removed file 'Theory'. The goal is to document
tzdb theory more accessibly.

The zic man page now documents abbreviation rules.

tz-link.htm now covers how to apply tzdata changes to clients.
(Thanks to Jorge F��bregas for the AIX link.) It also mentions MySQL.

The leap-seconds.list URL has been updated to something that is
more reliable for tzdb. (Thanks to Tim Parenti and Brian Inglis.)

merge 2015f

merge tzcode2015e:

Changes affecting code

When displaying data, tzselect converts it to the current locale's
encoding if the iconv command works. (Problem reported by random832.)

tzselect no longer mishandles Dominica, fixing a bug introduced
in Release 2014f. (Problem reported by Owen Leibman.)

zic -l no longer fails when compiled with -DTZDEFAULT=\"/etc/localtime\".
This fixes a bug introduced in Release 2014f.
(Problem reported by Leonardo Chiquitto.)

Sync with tzcode2014h

merge tzcode2014f via patch

branches: 1.22.2;
welcome to 2014d; zic big bang fixes:
some programs did not handle large negative time_t values well (gnome)

branches: 1.21.2;
Welcome to tzcode 2013e:

Changes affecting API

The 'zic' command now outputs a dummy transition when far-future
data can't be summarized using a TZ string, and uses a 402-year
window rather than a 400-year window. For the current data, this
affects only the Asia/Tehran file. It does not affect any of the
time stamps that this file represents, so zdump outputs the same
information as before. (Thanks to Andrew Main (Zefram).)

The 'date' command has a new '-r' option, which lets you specify
the integer time to display, a la FreeBSD.

The 'tzselect' command has two new options '-c' and '-n', which lets you
select a zone based on latitude and longitude.

The 'zic' command's '-v' option now warns about constructs that
require the new version-3 binary file format. (Thanks to Arthur
David Olson for the suggestion.)

Support for floating-point time_t has been removed.
It was always dicey, and POSIX no longer requires it.
(Thanks to Eric Blake for suggesting to the POSIX committee to
remove it, and thanks to Alan Barrett, Clive D.W. Feather, Andy
Heninger, Arthur David Olson, and Alois Treindl, for reporting
bugs and elucidating some of the corners of the old floating-point
implementation.)

The signatures of 'offtime', 'timeoff', and 'gtime' have been
changed back to the old practice of using 'long' to represent UT
offsets. This had been inadvertently and mistakenly changed to
'int_fast32_t'. (Thanks to Christos Zoulos.)

The code avoids undefined behavior on integer overflow in some
more places, including gmtime, localtime, mktime and zdump.

Changes affecting the zdump utility

zdump now outputs "UT" when referring to Universal Time, not "UTC".
"UTC" does not make sense for time stamps that predate the introduction
of UTC, whereas "UT", a more-generic term, does. (Thanks to Steve Allen
for clarifying UT vs UTC.)

Data changes affecting behavior of tzselect and similar programs

Country code BQ is now called the more-common name "Caribbean Netherlands"
rather than the more-official "Bonaire, St Eustatius & Saba".

Remove from zone.tab the names America/Montreal, America/Shiprock,
and Antarctica/South_Pole, as they are equivalent to existing
same-country-code zones for post-1970 time stamps. The data for
these names are unchanged, so the names continue to work as before.

Changes affecting code internals

zic -c now runs way faster on 64-bit hosts when given large numbers.

zic now uses vfprintf to avoid allocating and freeing some memory.

tzselect now computes the list of continents from the data,
rather than have it hard-coded.

Minor changes pacify GCC 4.7.3 and GCC 4.8.1.

Changes affecting the build procedure

The 'leapseconds' file is now generated automatically from a
new file 'leap-seconds.list', which is a copy of
<ftp://time.nist.gov/pub/leap-seconds.list>.
A new source file 'leapseconds.awk' implements this.
The goal is simplification of the future maintenance of 'leapseconds'.

When building the 'posix' or 'right' subdirectories, if the
subdirectory would be a copy of the default subdirectory, it is
now made a symbolic link if that is supported. This saves about
2 MB of file system space.

The links America/Shiprock and Antarctica/South_Pole have been
moved to the 'backward' file. This affects only nondefault builds
that omit 'backward'.

Changes affecting documentation and commentary

Changes to the 'tzfile' man page

It now mentions that the binary file format may be extended in
future versions by appending data.

It now refers to the 'zdump' and 'zic' man pages.

Changes to the 'zic' man page

It lists conditions that elicit a warning with '-v'.

It says that the behavior is unspecified when duplicate names
are given, or if the source of one link is the target of another.

Its examples are updated to match the latest data.

The definition of white space has been clarified slightly.
(Thanks to Michael Deckers.)

Changes to the 'Theory' file

There is a new section about the accuracy of the tz database,
describing the many ways that errors can creep in, and
explaining why so many of the pre-1970 time stamps are wrong or
misleading (thanks to Steve Allen, Lester Caine, and Garrett
Wollman for discussions that contributed to this).

The 'Theory' file describes LMT better (this follows a
suggestion by Guy Harris).

It refers to the 2013 edition of POSIX rather than the 2004 edition.

It's mentioned that excluding 'backward' should not affect the
other data, and it suggests at least one zone.tab name per
inhabited country (thanks to Stephen Colebourne).

Some longstanding restrictions on names are documented, e.g.,
'America/New_York' precludes 'America/New_York/Bronx'.

It gives more reasons for the 1970 cutoff.

It now mentions which time_t variants are supported, such as
signed integer time_t. (Thanks to Paul Goyette for reporting
typos in an experimental version of this change.)

(Thanks to Philip Newton for correcting typos in these changes.)

Documentation and commentary is more careful to distinguish UT in
general from UTC in particular. (Thanks to Steve Allen.)

Add a better source for the Zurich 1894 transition.
(Thanks to Pierre-Yves Berger.)

Update shapefile citations in tz-link.htm. (Thanks to Guy Harris.)

branches: 1.20.2;
merge 2012e

branches: 1.19.2;
bring in the 2011i changes.

New sentence, new line.

Fix up mix of man(7)/mdoc(7).

Import tzcode2009k.
- now understands 64bit time_t and 64bit data in timezone files.
- localtime(), gmtime(), asctime() and ctime() may now fail with
a NULL result if time_t cannot be represented by struct tm.

Fix preamble to match order set out by mdoc(7). Discussed with wiz.

branches: 1.14.42;
Merge tzcode2003e.

Merge tzcode2003d.

Use a better width argument.

Generate <>& symbolically. I'm avoiding .../dist/... directories for now.

mdoc'ify

branches: 1.9.6;
Merge tzcode1999i.

branches: 1.8.6;
Merge tzcode1998h.

sync with tzcode1998a

Sync with tzcode1997e

alternate -> alternative, per PR 2643

sync with tzcode96a

/usr/local/etc/zoneinfo -> /usr/share/zoneinfo; PR #1398

branches: 1.2.2;
Added NetBSD Id.
Removed "new" from newctime(3) references.

branches: 1.1.1;
Initial revision

Fix yet another wording (editing) botch noticed by uwe@

zic(8): missed a .Ql

Fix a wording botch noticed by uwe@ (and one more smaller one), and
a few more markup issues. While here, consistemntly use minus when
minus is meant, rather that just using a hyphen.

zic(8): more markup fixes

Still need to go over the tables.

More markup fixes. This man page remains exceedingly ugly (particularly
relating to vertical space - which often is missing where it would be
better if it weren't, or is present and wasteful/ugly).

PR/57757: Izumi Tsutsui: Fix markup errors

Update tzcode from 2022g to 2023c:

Release 2023c - 2023-03-28 12:42:14 -0700

Release 2023b - 2023-03-23 19:50:38 -0700

Release 2023a - 2023-03-22 12:39:33 -0700

Changes to code

You can now tell tzselect local time, to simplify later choices.
Select the 'time' option in its first prompt.

You can now compile with -DTZNAME_MAXIMUM=N to limit time zone
abbreviations to N bytes (default 255). The reference runtime
library now rejects POSIX-style TZ strings that contain longer
abbreviations, treating them as UTC. Previously the limit was
platform dependent and abbreviations were silently truncated to
16 bytes even when the limit was greater than 16.

The code by default is now designed for C99 or later. To build in
a C89 environment, compile with -DPORT_TO_C89. To support C89
callers of the tzcode library, compile with -DSUPPORT_C89. The
two new macros are transitional aids planned to be removed in a
future version, when C99 or later will be required.

The code now builds again on pre-C99 platforms, if you compile
with -DPORT_TO_C89. This fixes a bug introduced in 2022f.

On C23-compatible platforms tzcode no longer uses syntax like
'static [[noreturn]] void usage(void);'. Instead, it uses
'[[noreturn]] static void usage(void);' as strict C23 requires.
(Problem reported by Houge Langley.)

The code's functions now constrain their arguments with the C
'restrict' keyword consistently with their documentation.
This may allow future optimizations.

zdump again builds standalone with ckdadd and without setenv,
fixing a bug introduced in 2022g. (Problem reported by panic.)

leapseconds.awk can now process a leap seconds file that never
expires; this might be useful if leap seconds are discontinued.

Changes to commentary

tz-link.html has a new section "Coordinating with governments and
distributors". (Thanks to Neil Fuller for some of the text.)

To improve tzselect diagnostics, zone1970.tab's comments column is
now limited to countries that have multiple timezones.

Note that leap seconds are planned to be discontinued by 2035.

Fix formatting corruption for manpages from tzcode.

Comment out .TH macros, that cause mandoc(1) to run into man(7) mode.

Merge in 2022g:

Although tzcode still works with C89, bugs found in recent routine
maintenance indicate that bitrot has set in and that in practice
C89 is no longer used to build tzcode. As it is a maintenance
burden, support for C89 is planned to be removed soon. Instead,
please use compilers compatible with C99, C11, C17, or C23.

timegm, which tzcode implemented in 1989, will finally be
standardized 34 years later as part of C23, so timegm is now
supported even if STD_INSPIRED is not defined.

Fix bug in zdump's tzalloc emulation on hosts that lack tm_zone.
(Problem reported by ��o��n Tr���n C��ng Danh.)

Fix bug in zic on hosts where malloc(0) yields NULL on success.
(Problem reported by Tim McBrayer for AIX 6.1.)

Fix zic configuration to avoid linkage failures on some platforms.
(Problems reported by Gilmore Davidson and Igor Ivanov.)

Work around MS-Windows nmake incompatibility with POSIX.
(Problem reported by Manuela Friedrich.)

Port mktime and strftime to debugging platforms where accessing
uninitialized data has undefined behavior (strftime problem
reported by Robert Elz).

Check more carefully for unlikely integer overflows, preferring
C23 <stdckdint.h> to overflow checking by hand, as the latter has
had obscure bugs.

Update to tzcode2022f

Changes to code

zic now supports links to links regardless of input line order.
For example, if Australia/Sydney is a Zone, the lines
Link Australia/Canberra Australia/ACT
Link Australia/Sydney Australia/Canberra
now work correctly, even though the shell commands
ln Australia/Canberra Australia/ACT
ln Australia/Sydney Australia/Canberra
would fail because the first command attempts to use a link
Australia/Canberra that does not exist until after the second
command is executed. Previously, zic had unspecified behavior if
a Link line's target was another link, and zic often misbehaved if
a Link line's target was a later Link line.

Fix line number in zic's diagnostic for a link to a link.

Fix a bug that caused localtime to mishandle timestamps starting
in the year 2438 when reading data generated by 'zic -b fat' when
distant-future DST transitions occur at times given in standard
time or in UT, not the usual case of local time. This occurs when
the corresponding .zi Rule lines specify DST transitions with TO
columns of 'max' and AT columns that end in 's' or 'u'. The
number 2438 comes from the 32-bit limit in the year 2038, plus the
400-year Gregorian cycle. (Problem reported by Bradley White.)

On glibc 2.34 and later, which optionally supports 64-bit time_t
on platforms like x86 where time_t was traditionally 32 bits,
default time_t to 64 instead of 32 bits. This lets functions like
localtime support timestamps after the year 2038, and fixes
year-2038 problems in zic when accessing files dated after 2038.
To continue to limit time_t to 32 bits on these platforms, use
"make CFLAGS='-D_TIME_BITS=32'".

In C code, do not enable large-file support on platforms like AIX
and macOS that no longer need it now that tzcode does not use
off_t or related functions like 'stat'. Large-file support is
still enabled by default on GNU/Linux, as it is needed for 64-bit
time_t support.

In C code, prefer C23 keywords to pre-C23 macros for alignof,
bool, false, and true. Also, use the following C23 features if
available: __has_include, unreachable.

zic no longer works around Qt bug 53071, as the relevant Qt
releases have been out of support since 2019. This change affects
only fat TZif files, as thin files never had the workaround.

zdump no longer modifies the environ vector when compiled on
platforms lacking tm_zone or when compiled with -DUSE_LTZ=0.
This avoid undefined behavior on POSIX platforms.

add missing text.

Welcome to 2022b:

zic has a new option '-R @N' to output explicit transitions < N.
(Need suggested by Almaz Mingaleev.)

'zic -r @N' no longer outputs bad data when N < first transition.
(Problem introduced in 2021d and reported by Peter Krefting.)

zic now checks its input for NUL bytes and unterminated lines, and
now supports input line lengths up to 2048 (not 512) bytes.

gmtime and related code now use the abbreviation "UTC" not "GMT".
POSIX is being revised to require this.

When tzset and related functions set vestigial static variables
like tzname, they now prefer specified timestamps to unspecified ones.
(Problem reported by Almaz Mingaleev.)

zic no longer complains "can't determine time zone abbreviation to
use just after until time" when a transition to a new standard
time occurs simultanously with the first DST fallback transition.

Change to code and documentation from 2021a -> 2021e

Release 2021e - 2021-10-21 18:41:00 -0700

Changes to code

none


Release 2021d - 2021-10-15 13:48:18 -0700

Changes to code

'zic -r' now uses "-00" time zone abbreviations for intervals
with UT offsets that are unspecified due to -r truncation.
This implements a change in draft Internet RFC 8536bis.


Release 2021c - 2021-10-01 14:21:49 -0700

Changes to code

Fix a bug in 'zic -b fat' that caused old timestamps to be
mishandled in 32-bit-only readers (problem reported by Daniel
Fischer).

Changes to documentation

Distribute the SECURITY file (problem reported by Andreas Radke).


Release 2021b - 2021-09-24 16:23:00 -0700

Changes to maintenance procedure

The new file SECURITY covers how to report security-related bugs.

Several backward-compatibility links have been moved to the
'backward' file. These links, which range from Africa/Addis_Ababa
to Pacific/Saipan, are only for compatibility with now-obsolete
guidelines suggesting an entry for every ISO 3166 code.
The intercontinental convenience links Asia/Istanbul and
Europe/Nicosia have also been moved to 'backward'.

Changes to code

zic now creates each output file or link atomically,
possibly by creating a temporary file and then renaming it.
This avoids races where a TZ setting would temporarily stop
working while zic was installing a replacement file or link.

zic -L no longer omits the POSIX TZ string in its output.
Starting with 2020a, zic -L truncated its output according to the
"Expires" directive or "#expires" comment in the leapseconds file.
The resulting TZif files omitted daylight saving transitions after
the leap second table expired, which led to far less-accurate
predictions of times after the expiry. Although future timestamps
cannot be converted accurately in the presence of leap seconds, it
is more accurate to convert near-future timestamps with a few
seconds error than with an hour error, so zic -L no longer
truncates output in this way.

Instead, when zic -L is given the "Expires" directive, it now
outputs the expiration by appending a no-change entry to the leap
second table. Although this should work well with most TZif
readers, it does not conform to Internet RFC 8536 and some pickier
clients (including tzdb 2017c through 2021a) reject it, so
"Expires" directives are currently disabled by default. To enable
them, set the EXPIRES_LINE Makefile variable. If a TZif file uses
this new feature it is marked with a new TZif version number 4,
a format intended to be documented in a successor to RFC 8536.

zic -L LEAPFILE -r @LO no longer generates an invalid TZif file
that omits leap second information for the range LO..B when LO
falls between two leap seconds A and B. Instead, it generates a
TZif version 4 file that represents the previously-missing
information.

The TZif reader now allows the leap second table to begin with a
correction other than -1 or +1, and to contain adjacent
transitions with equal corrections. This supports TZif version 4.

The TZif reader now lets leap seconds occur less than 28 days
apart. This supports possible future TZif extensions.

Fix bug that caused 'localtime' etc. to crash when TZ was
set to a all-year DST string like "EST5EDT4,0/0,J365/25" that does
not conform to POSIX but does conform to Internet RFC 8536.

Fix another bug that caused 'localtime' etc. to crash when TZ was
set to a POSIX-conforming but unusual TZ string like
"EST5EDT4,0/0,J365/0", where almost all the year is DST.

Fix yet another bug that caused 'localtime' etc. to mishandle slim
TZif files containing leap seconds after the last explicit
transition in the table, or when handling far-future timestamps
in slim TZif files lacking leap seconds.

Fix localtime misbehavior involving positive leap seconds.
This change affects only behavior for "right" system time,
which contains leap seconds, and only if the UT offset is
not a multiple of 60 seconds when a positive leap second occurs.
(No such timezone exists in tzdb, luckily.) Without the fix,
the timestamp was ambiguous during a positive leap second.
With the fix, any seconds occurring after a positive leap second
and within the same localtime minute are counted through 60, not
through 59; their UT offset (tm_gmtoff) is the same as before.
Here is how the fix affects timestamps in a timezone with UT
offset +01:23:45 (5025 seconds) and with a positive leap second at
1972-06-30 23:59:60 UTC (78796800):

time_t without the fix with the fix
78796800 1972-07-01 01:23:45 1972-07-01 01:23:45 (leap second)
78796801 1972-07-01 01:23:45 1972-07-01 01:23:46
...
78796815 1972-07-01 01:23:59 1972-07-01 01:23:60
78796816 1972-07-01 01:24:00 1972-07-01 01:24:00

Fix an unlikely bug that caused 'localtime' etc. to misbehave if
civil time changes a few seconds before time_t wraps around, when
leap seconds are enabled.

Fix bug in zic -r; in some cases, the dummy time type after the
last time transition disagreed with the TZ string, contrary to
Internet RFC 8563 section 3.3.

Fix a bug with 'zic -r @X' when X is a negative leap second that
has a nonnegative correction. Without the fix, the output file
was truncated so that X appeared to be a positive leap second.
Fix a similar, even-less-likely bug when truncating at a positive
leap second that has a nonpositive correction.

zic -r now reports an error if given rolling leap seconds, as this
usage has never generally worked and is evidently unused.

zic now generates a POSIX-conforming TZ string for TZif files
where all-year DST is predicted for the indefinite future.
For example, for all-year Eastern Daylight Time, zic now generates
"XXX3EDT4,0/0,J365/23" where it previously generated
"EST5EDT,0/0,J365/25" or "". (Thanks to Michael Deckers for
noting the possibility of POSIX conformance.)

zic.c no longer requires sys/wait.h (thanks to spazmodius for
noting it wasn't needed).

When reading slim TZif files, zdump no longer mishandles leap
seconds on the rare platforms where time_t counts leap seconds,
fixing a bug introduced in 2014g.

zdump -v now outputs timestamps at boundaries of what localtime
and gmtime can represent, instead of the less-useful timestamps
one day after the minimum and one day before the maximum.
(Thanks to Arthur David Olson for prototype code, and to Manuela
Friedrich for debugging help.)

zdump's -c and -t options are now consistently inclusive for the
lower time bound and exclusive for the upper. Formerly they were
inconsistent. (Confusion noted by Martin Burnicki.)

Changes to build procedure

You can now compile with -DHAVE_MALLOC_ERRNO=0 to port to
non-POSIX hosts where malloc doesn't set errno.
(Problem reported by Jan Engelhardt.)

Changes to documentation

tzfile.5 better matches a draft successor to RFC 8536
<https://datatracker.ietf.org/doc/draft-murchison-rfc8536bis/01/>.

Merge tzcode-2021a
- No comments in the changelog about the code changes.

Merge tzcode2020b (except we keep tzsetwall(3) for now for compatibility,
and we were "slim" already)

Support for zic's long-obsolete '-y YEARISTYPE' option has been
removed and, with it, so has support for the TYPE field in Rule
lines, which is now reserved for compatibility with earlier zic.
These features were previously deprecated in release 2015f.
(Thanks to Tim Parenti.)

zic now defaults to '-b slim' instead of to '-b fat'.

zic's new '-l -' and '-p -' options uninstall any existing
localtime and posixrules files, respectively.

The undocumented and ineffective tzsetwall function has been
removed.

Bring in 2020a

Sync with 2019b:

zic's new -b option supports a way to control data bloat and to
test for year-2038 bugs in software that reads TZif files.
'zic -b fat' and 'zic -b slim' generate larger and smaller output;
for example, changing from fat to slim shrinks the Europe/London
file from 3648 to 1599 bytes, saving about 56%. Fat and slim
files represent the same set of timestamps and use the same TZif
format as documented in tzfile(5) and in Internet RFC 8536.
Fat format attempts to work around bugs or incompatibilities in
older software, notably software that mishandles 64-bit TZif data
or uses obsolete TZ strings like "EET-2EEST" that lack DST rules.
Slim format is more efficient and does not work around 64-bit bugs
or obsolete TZ strings. Currently zic defaults to fat format
unless you compile with -DZIC_BLOAT_DEFAULT=\"slim\"; this
out-of-the-box default is intended to change in future releases
as the buggy software often mishandles timestamps anyway.

zic no longer treats a set of rules ending in 2037 specially.
Previously, zic assumed that such a ruleset meant that future
timestamps could not be predicted, and therefore omitted a
POSIX-like TZ string in the TZif output. The old behavior is no
longer needed for current tzdata, and caused problems with newlib
when used with older tzdata (reported by David Gauchard).

zic no longer generates some artifact transitions. For example,
Europe/London no longer has a no-op transition in January 1996.

merge 2019a

Changes to code

zic now has an -r option to limit the time range of output data.
For example, 'zic -r @1000000000' limits the output data to
timestamps starting 1000000000 seconds after the Epoch.
This helps shrink output size and can be useful for applications
not needing the full timestamp history, such as TZDIST truncation;
see Internet RFC 8536 section 5.1. (Inspired by a feature request
from Christopher Wong, helped along by bug reports from Wong and
from Tim Parenti.)

Changes to documentation

Mention Internet RFC 8536 (February 2019), which documents TZif.

tz-link.html now cites tzdata-meta
<https://tzdata-meta.timtimeonline.com/>.

Welcome tzcode-2018g

Changes to code

When generating TZif files with leap seconds, zic no longer uses a
format that trips up older 32-bit clients, fixing a bug introduced
in 2018f. (Reported by Daniel Fischer.) Also, the zic workaround
for QTBUG-53071 now also works for TZif files with leap seconds.

The translator to rearguard format now rewrites the line
"Rule Japan 1948 1951 - Sep Sat>=8 25:00 0 S" to
"Rule Japan 1948 1951 - Sep Sun>=9 1:00 0 S".
This caters to zic before 2007 and to Oracle TZUpdater 2.2.0
and earlier. (Reported by Christos Zoulas.)

Changes to documentation

tzfile.5 has new sections on interoperability issues.

Update to 2018f:

Changes to code

zic now always generates TZif files where time type 0 is used for
timestamps before the first transition. This simplifies the
reading of TZif files and should not affect behavior of existing
TZif readers because the same set of time types is used; only
their internal indexes may have changed. This affects only the
legacy zones EST5EDT, CST6CDT, MST7MDT, PST8PDT, CET, MET, and
EET, which previously used nonzero types for these timestamps.

Because of the type 0 change, zic no longer outputs a dummy
transition at time -2**59 (before the Big Bang), as clients should
no longer need this to handle historical timestamps correctly.
This reverts a change introduced in 2013d and shrinks most TZif
files by a few bytes.

zic now supports negative time-of-day in Rule and Leap lines, e.g.,
"Rule X min max - Apr lastSun -6:00 1:00 -" means the transition
occurs at 18:00 on the Saturday before the last Sunday in April.
This behavior was documented in 2018a but the code did not
entirely match the documentation.

localtime.c no longer requires at least one time type in TZif
files that lack transitions or have a POSIX-style TZ string. This
future-proofs the code against possible future extensions to the
format that would allow TZif files with POSIX-style TZ strings and
without transitions or time types.

A read-access subscript error in localtime.c has been fixed.
It could occur only in TZif files with timecnt == 0, something that
does not happen in practice now but could happen in future versions.

localtime.c no longer ignores TZif POSIX-style TZ strings that
specify only standard time. Instead, these TZ strings now
override the default time type for timestamps after the last
transition (or for all time stamps if there are no transitions),
just as DST strings specifying DST have always done.

leapseconds.awk now outputs "#updated" and "#expires" comments,
and supports leap seconds at the ends of months other than June
and December. (Inspired by suggestions from Chris Woodbury.)

Changes to documentation

New restrictions: A Rule name must start with a character that
is neither an ASCII digit nor "-" nor "+", and an unquoted name
should not use characters in the set "!$%&'()*,/:;<=>?@[\]^`{|}~".
The latter restriction makes room for future extensions (a
possibility noted by Tom Lane).

tzfile.5 now documents what time types apply before the first and
after the last transition, if any.

Documentation now uses the spelling "timezone" for a TZ setting
that determines timestamp history, and "time zone" for a
geographic region currently sharing the same standard time.

The name "TZif" is now used for the tz binary data format.

tz-link.htm now mentions the A0 TimeZone Migration utilities.
(Thanks to Aldrin Martoq for the link.)

branches: 1.29.2;
Merge 2018e

Changes to code

zic now accepts subsecond precision in expressions like
00:19:32.13, which is approximately the legal time of the
Netherlands from 1835 to 1937. However, because it is
questionable whether the few recorded uses of non-integer offsets
had subsecond precision in practice, there are no plans for tzdata
to use this feature. (Thanks to Steve Allen for pointing out
the limitations of historical data in this area.)

The code is a bit more portable to MS-Windows. Installers can
compile with -DRESERVE_STD_EXT_IDS on MS-Windows platforms that
reserve identifiers like 'localtime'. (Thanks to Manuela
Friedrich).

Changes to documentation and commentary

theory.html now outlines tzdb's extensions to POSIX's model for
civil time, and has a section "POSIX features no longer needed"
that lists POSIX API components that are now vestigial.
(From suggestions by Steve Summit.) It also better distinguishes
time zones from tz regions. (From a suggestion by Guy Harris.)

Commentary is now more consistent about using the phrase "daylight
saving time", to match the C name tm_isdst. Daylight saving time
need not occur in summer, and need not have a positive offset from
standard time.

Commentary about historical transitions in Uruguay has been expanded
with links to many relevant legal documents.
(Thanks to Tim Parenti.)

Commentary now uses some non-ASCII characters with Unicode value
less than U+0100, as they can be useful and should work even with
older editors such as XEmacs.

branches: 1.28.2;
Merge tzcode2018c [ changelog with changes to tzdata sections removed ]

Release 2018c - 2018-01-22 23:00:44 -0800

Changes to build procedure

The build procedure now works around mawk 1.3.3's lack of support
for character class expressions. (Problem reported by Ohyama.)


Release 2018b - 2018-01-17 23:24:48 -0800

Changes to build procedure

The distribution now contains the file 'pacificnew' again.
This file was inadvertantly omitted in the 2018a distribution.
(Problem reported by Matias Fonzo.)


Release 2018a - 2018-01-12 22:29:21 -0800

Changes to build procedure

The default installation locations have been changed to mostly
match Debian circa 2017, instead of being designed as an add-on to
4.3BSD circa 1986. This affects the Makefile macros TOPDIR,
TZDIR, MANDIR, and LIBDIR. New Makefile macros TZDEFAULT, USRDIR,
USRSHAREDIR, BINDIR, ZDUMPDIR, and ZICDIR let installers tailor
locations more precisely. (This responds to suggestions from
Brian Inglis and from Steve Summit.)

The default installation procedure no longer creates the
backward-compatibility link US/Pacific-New, which causes
confusion during user setup (e.g., see Debian bug 815200).
Use 'make BACKWARD="backward pacificnew"' to create the link
anyway, for now. Eventually we plan to remove the link entirely.

tzdata.zi now contains a version-number comment.
(Suggested by Tom Lane.)

The Makefile now quotes values like BACKWARD more carefully when
passing them to the shell. (Problem reported by Zefram.)

Builders no longer need to specify -DHAVE_SNPRINTF on platforms
that have snprintf and use pre-C99 compilers. (Problem reported
by Jon Skeet.)

Changes to code

zic has a new option -t FILE that specifies the location of the
file that determines local time when TZ is unset. The default for
this location can be configured via the new TZDEFAULT makefile
macro, which defaults to /etc/localtime.

Diagnostics and commentary now distinguish UT from UTC more
carefully; see theory.html for more information about UT vs UTC.

zic has been ported to GCC 8's -Wstringop-truncation option.
(Problem reported by Martin Sebor.)

Changes to documentation and commentary

The zic man page now documents the longstanding behavior that
times and years can be out of the usual range, with negative times
counting backwards from midnight and with year 0 preceding year 1.
(Problem reported by Michael Deckers.)

The theory.html file now mentions the POSIX limit of six chars
per abbreviation, and lists alphabetic abbreviations used.

The files tz-art.htm and tz-link.htm have been renamed to
tz-art.html and tz-link.html, respectively, for consistency with
other file names and to simplify web server configuration.

Welcome to 2017c:

zic and the reference runtime now reject multiple leap seconds
within 28 days of each other, or leap seconds before the Epoch.
As a result, support for double leap seconds, which was
obsolescent and undocumented, has been removed. Double leap
seconds were an error in the C89 standard; they have never existed
in civil timekeeping. (Thanks to Robert Elz and Bradley White for
noticing glitches in the code that uncovered this problem.)

zic now warns about use of the obsolescent and undocumented -y
option, and about use of the obsolescent TYPE field of Rule lines.

zic now allows unambiguous abbreviations like "Sa" and "Su" for
weekdays; formerly it rejected them due to a bug. Conversely, zic
no longer considers non-prefixes to be abbreviations; for example,
it no longer accepts "lF" as an abbreviation for "lastFriday".
Also, zic warns about the undocumented usage with a "last-"
prefix, e.g., "last-Fri".

Similarly, zic now accepts the unambiguous abbreviation "L" for
"Link" in ordinary context and for "Leap" in leap-second context.
Conversely, zic no longer accepts non-prefixes such as "La" as
abbreviations for words like "Leap".

zic no longer accepts leap second lines in ordinary input, or
ordinary lines in leap second input. Formerly, zic sometimes
warned about this undocumented usage and handled it incorrectly.

The new macro HAVE_TZNAME governs whether the tzname external
variable is exported, instead of USG_COMPAT. USG_COMPAT now
governs only the external variables "timezone" and "daylight".
This change is needed because the three variables are not in the
same category: although POSIX requires tzname, it specifies the
other two variables as optional. Also, USG_COMPAT is now 1 or 0:
if not defined, the code attempts to guess it from other macros.

localtime.c and difftime.c no longer require stdio.h, and .c files
other than zic.c no longer require sys/wait.h.

zdump.c no longer assumes snprintf. (Reported by Jonathan Leffler.)

Calculation of time_t extrema works around a bug in GCC 4.8.4
(Reported by Stan Shebs and Joseph Myers.)

zic.c no longer mistranslates formats of line numbers in non-English
locales. (Problem reported by Benno Schulenberg.)

Several minor changes have been made to the code to make it a
bit easier to port to MS-Windows and Solaris. (Thanks to Kees
Dekker for reporting the problems.)

Changes to documentation and commentary

The two new files 'theory.html' and 'calendars' contain the
contents of the removed file 'Theory'. The goal is to document
tzdb theory more accessibly.

The zic man page now documents abbreviation rules.

tz-link.htm now covers how to apply tzdata changes to clients.
(Thanks to Jorge F��bregas for the AIX link.) It also mentions MySQL.

The leap-seconds.list URL has been updated to something that is
more reliable for tzdb. (Thanks to Tim Parenti and Brian Inglis.)

merge 2015f

merge tzcode2015e:

Changes affecting code

When displaying data, tzselect converts it to the current locale's
encoding if the iconv command works. (Problem reported by random832.)

tzselect no longer mishandles Dominica, fixing a bug introduced
in Release 2014f. (Problem reported by Owen Leibman.)

zic -l no longer fails when compiled with -DTZDEFAULT=\"/etc/localtime\".
This fixes a bug introduced in Release 2014f.
(Problem reported by Leonardo Chiquitto.)

Sync with tzcode2014h

merge tzcode2014f via patch

branches: 1.22.2;
welcome to 2014d; zic big bang fixes:
some programs did not handle large negative time_t values well (gnome)

branches: 1.21.2;
Welcome to tzcode 2013e:

Changes affecting API

The 'zic' command now outputs a dummy transition when far-future
data can't be summarized using a TZ string, and uses a 402-year
window rather than a 400-year window. For the current data, this
affects only the Asia/Tehran file. It does not affect any of the
time stamps that this file represents, so zdump outputs the same
information as before. (Thanks to Andrew Main (Zefram).)

The 'date' command has a new '-r' option, which lets you specify
the integer time to display, a la FreeBSD.

The 'tzselect' command has two new options '-c' and '-n', which lets you
select a zone based on latitude and longitude.

The 'zic' command's '-v' option now warns about constructs that
require the new version-3 binary file format. (Thanks to Arthur
David Olson for the suggestion.)

Support for floating-point time_t has been removed.
It was always dicey, and POSIX no longer requires it.
(Thanks to Eric Blake for suggesting to the POSIX committee to
remove it, and thanks to Alan Barrett, Clive D.W. Feather, Andy
Heninger, Arthur David Olson, and Alois Treindl, for reporting
bugs and elucidating some of the corners of the old floating-point
implementation.)

The signatures of 'offtime', 'timeoff', and 'gtime' have been
changed back to the old practice of using 'long' to represent UT
offsets. This had been inadvertently and mistakenly changed to
'int_fast32_t'. (Thanks to Christos Zoulos.)

The code avoids undefined behavior on integer overflow in some
more places, including gmtime, localtime, mktime and zdump.

Changes affecting the zdump utility

zdump now outputs "UT" when referring to Universal Time, not "UTC".
"UTC" does not make sense for time stamps that predate the introduction
of UTC, whereas "UT", a more-generic term, does. (Thanks to Steve Allen
for clarifying UT vs UTC.)

Data changes affecting behavior of tzselect and similar programs

Country code BQ is now called the more-common name "Caribbean Netherlands"
rather than the more-official "Bonaire, St Eustatius & Saba".

Remove from zone.tab the names America/Montreal, America/Shiprock,
and Antarctica/South_Pole, as they are equivalent to existing
same-country-code zones for post-1970 time stamps. The data for
these names are unchanged, so the names continue to work as before.

Changes affecting code internals

zic -c now runs way faster on 64-bit hosts when given large numbers.

zic now uses vfprintf to avoid allocating and freeing some memory.

tzselect now computes the list of continents from the data,
rather than have it hard-coded.

Minor changes pacify GCC 4.7.3 and GCC 4.8.1.

Changes affecting the build procedure

The 'leapseconds' file is now generated automatically from a
new file 'leap-seconds.list', which is a copy of
<ftp://time.nist.gov/pub/leap-seconds.list>.
A new source file 'leapseconds.awk' implements this.
The goal is simplification of the future maintenance of 'leapseconds'.

When building the 'posix' or 'right' subdirectories, if the
subdirectory would be a copy of the default subdirectory, it is
now made a symbolic link if that is supported. This saves about
2 MB of file system space.

The links America/Shiprock and Antarctica/South_Pole have been
moved to the 'backward' file. This affects only nondefault builds
that omit 'backward'.

Changes affecting documentation and commentary

Changes to the 'tzfile' man page

It now mentions that the binary file format may be extended in
future versions by appending data.

It now refers to the 'zdump' and 'zic' man pages.

Changes to the 'zic' man page

It lists conditions that elicit a warning with '-v'.

It says that the behavior is unspecified when duplicate names
are given, or if the source of one link is the target of another.

Its examples are updated to match the latest data.

The definition of white space has been clarified slightly.
(Thanks to Michael Deckers.)

Changes to the 'Theory' file

There is a new section about the accuracy of the tz database,
describing the many ways that errors can creep in, and
explaining why so many of the pre-1970 time stamps are wrong or
misleading (thanks to Steve Allen, Lester Caine, and Garrett
Wollman for discussions that contributed to this).

The 'Theory' file describes LMT better (this follows a
suggestion by Guy Harris).

It refers to the 2013 edition of POSIX rather than the 2004 edition.

It's mentioned that excluding 'backward' should not affect the
other data, and it suggests at least one zone.tab name per
inhabited country (thanks to Stephen Colebourne).

Some longstanding restrictions on names are documented, e.g.,
'America/New_York' precludes 'America/New_York/Bronx'.

It gives more reasons for the 1970 cutoff.

It now mentions which time_t variants are supported, such as
signed integer time_t. (Thanks to Paul Goyette for reporting
typos in an experimental version of this change.)

(Thanks to Philip Newton for correcting typos in these changes.)

Documentation and commentary is more careful to distinguish UT in
general from UTC in particular. (Thanks to Steve Allen.)

Add a better source for the Zurich 1894 transition.
(Thanks to Pierre-Yves Berger.)

Update shapefile citations in tz-link.htm. (Thanks to Guy Harris.)

branches: 1.20.2;
merge 2012e

branches: 1.19.2;
bring in the 2011i changes.

New sentence, new line.

Fix up mix of man(7)/mdoc(7).

Import tzcode2009k.
- now understands 64bit time_t and 64bit data in timezone files.
- localtime(), gmtime(), asctime() and ctime() may now fail with
a NULL result if time_t cannot be represented by struct tm.

Fix preamble to match order set out by mdoc(7). Discussed with wiz.

branches: 1.14.42;
Merge tzcode2003e.

Merge tzcode2003d.

Use a better width argument.

Generate <>& symbolically. I'm avoiding .../dist/... directories for now.

mdoc'ify

branches: 1.9.6;
Merge tzcode1999i.

branches: 1.8.6;
Merge tzcode1998h.

sync with tzcode1998a

Sync with tzcode1997e

alternate -> alternative, per PR 2643

sync with tzcode96a

/usr/local/etc/zoneinfo -> /usr/share/zoneinfo; PR #1398

branches: 1.2.2;
Added NetBSD Id.
Removed "new" from newctime(3) references.

branches: 1.1.1;
Initial revision

Fix yet another wording (editing) botch noticed by uwe@

zic(8): missed a .Ql

Fix a wording botch noticed by uwe@ (and one more smaller one), and
a few more markup issues. While here, consistemntly use minus when
minus is meant, rather that just using a hyphen.

zic(8): more markup fixes

Still need to go over the tables.

More markup fixes. This man page remains exceedingly ugly (particularly
relating to vertical space - which often is missing where it would be
better if it weren't, or is present and wasteful/ugly).

PR/57757: Izumi Tsutsui: Fix markup errors

Update tzcode from 2022g to 2023c:

Release 2023c - 2023-03-28 12:42:14 -0700

Release 2023b - 2023-03-23 19:50:38 -0700

Release 2023a - 2023-03-22 12:39:33 -0700

Changes to code

You can now tell tzselect local time, to simplify later choices.
Select the 'time' option in its first prompt.

You can now compile with -DTZNAME_MAXIMUM=N to limit time zone
abbreviations to N bytes (default 255). The reference runtime
library now rejects POSIX-style TZ strings that contain longer
abbreviations, treating them as UTC. Previously the limit was
platform dependent and abbreviations were silently truncated to
16 bytes even when the limit was greater than 16.

The code by default is now designed for C99 or later. To build in
a C89 environment, compile with -DPORT_TO_C89. To support C89
callers of the tzcode library, compile with -DSUPPORT_C89. The
two new macros are transitional aids planned to be removed in a
future version, when C99 or later will be required.

The code now builds again on pre-C99 platforms, if you compile
with -DPORT_TO_C89. This fixes a bug introduced in 2022f.

On C23-compatible platforms tzcode no longer uses syntax like
'static [[noreturn]] void usage(void);'. Instead, it uses
'[[noreturn]] static void usage(void);' as strict C23 requires.
(Problem reported by Houge Langley.)

The code's functions now constrain their arguments with the C
'restrict' keyword consistently with their documentation.
This may allow future optimizations.

zdump again builds standalone with ckdadd and without setenv,
fixing a bug introduced in 2022g. (Problem reported by panic.)

leapseconds.awk can now process a leap seconds file that never
expires; this might be useful if leap seconds are discontinued.

Changes to commentary

tz-link.html has a new section "Coordinating with governments and
distributors". (Thanks to Neil Fuller for some of the text.)

To improve tzselect diagnostics, zone1970.tab's comments column is
now limited to countries that have multiple timezones.

Note that leap seconds are planned to be discontinued by 2035.

Fix formatting corruption for manpages from tzcode.

Comment out .TH macros, that cause mandoc(1) to run into man(7) mode.

Merge in 2022g:

Although tzcode still works with C89, bugs found in recent routine
maintenance indicate that bitrot has set in and that in practice
C89 is no longer used to build tzcode. As it is a maintenance
burden, support for C89 is planned to be removed soon. Instead,
please use compilers compatible with C99, C11, C17, or C23.

timegm, which tzcode implemented in 1989, will finally be
standardized 34 years later as part of C23, so timegm is now
supported even if STD_INSPIRED is not defined.

Fix bug in zdump's tzalloc emulation on hosts that lack tm_zone.
(Problem reported by ��o��n Tr���n C��ng Danh.)

Fix bug in zic on hosts where malloc(0) yields NULL on success.
(Problem reported by Tim McBrayer for AIX 6.1.)

Fix zic configuration to avoid linkage failures on some platforms.
(Problems reported by Gilmore Davidson and Igor Ivanov.)

Work around MS-Windows nmake incompatibility with POSIX.
(Problem reported by Manuela Friedrich.)

Port mktime and strftime to debugging platforms where accessing
uninitialized data has undefined behavior (strftime problem
reported by Robert Elz).

Check more carefully for unlikely integer overflows, preferring
C23 <stdckdint.h> to overflow checking by hand, as the latter has
had obscure bugs.

Update to tzcode2022f

Changes to code

zic now supports links to links regardless of input line order.
For example, if Australia/Sydney is a Zone, the lines
Link Australia/Canberra Australia/ACT
Link Australia/Sydney Australia/Canberra
now work correctly, even though the shell commands
ln Australia/Canberra Australia/ACT
ln Australia/Sydney Australia/Canberra
would fail because the first command attempts to use a link
Australia/Canberra that does not exist until after the second
command is executed. Previously, zic had unspecified behavior if
a Link line's target was another link, and zic often misbehaved if
a Link line's target was a later Link line.

Fix line number in zic's diagnostic for a link to a link.

Fix a bug that caused localtime to mishandle timestamps starting
in the year 2438 when reading data generated by 'zic -b fat' when
distant-future DST transitions occur at times given in standard
time or in UT, not the usual case of local time. This occurs when
the corresponding .zi Rule lines specify DST transitions with TO
columns of 'max' and AT columns that end in 's' or 'u'. The
number 2438 comes from the 32-bit limit in the year 2038, plus the
400-year Gregorian cycle. (Problem reported by Bradley White.)

On glibc 2.34 and later, which optionally supports 64-bit time_t
on platforms like x86 where time_t was traditionally 32 bits,
default time_t to 64 instead of 32 bits. This lets functions like
localtime support timestamps after the year 2038, and fixes
year-2038 problems in zic when accessing files dated after 2038.
To continue to limit time_t to 32 bits on these platforms, use
"make CFLAGS='-D_TIME_BITS=32'".

In C code, do not enable large-file support on platforms like AIX
and macOS that no longer need it now that tzcode does not use
off_t or related functions like 'stat'. Large-file support is
still enabled by default on GNU/Linux, as it is needed for 64-bit
time_t support.

In C code, prefer C23 keywords to pre-C23 macros for alignof,
bool, false, and true. Also, use the following C23 features if
available: __has_include, unreachable.

zic no longer works around Qt bug 53071, as the relevant Qt
releases have been out of support since 2019. This change affects
only fat TZif files, as thin files never had the workaround.

zdump no longer modifies the environ vector when compiled on
platforms lacking tm_zone or when compiled with -DUSE_LTZ=0.
This avoid undefined behavior on POSIX platforms.

add missing text.

Welcome to 2022b:

zic has a new option '-R @N' to output explicit transitions < N.
(Need suggested by Almaz Mingaleev.)

'zic -r @N' no longer outputs bad data when N < first transition.
(Problem introduced in 2021d and reported by Peter Krefting.)

zic now checks its input for NUL bytes and unterminated lines, and
now supports input line lengths up to 2048 (not 512) bytes.

gmtime and related code now use the abbreviation "UTC" not "GMT".
POSIX is being revised to require this.

When tzset and related functions set vestigial static variables
like tzname, they now prefer specified timestamps to unspecified ones.
(Problem reported by Almaz Mingaleev.)

zic no longer complains "can't determine time zone abbreviation to
use just after until time" when a transition to a new standard
time occurs simultanously with the first DST fallback transition.

Change to code and documentation from 2021a -> 2021e

Release 2021e - 2021-10-21 18:41:00 -0700

Changes to code

none


Release 2021d - 2021-10-15 13:48:18 -0700

Changes to code

'zic -r' now uses "-00" time zone abbreviations for intervals
with UT offsets that are unspecified due to -r truncation.
This implements a change in draft Internet RFC 8536bis.


Release 2021c - 2021-10-01 14:21:49 -0700

Changes to code

Fix a bug in 'zic -b fat' that caused old timestamps to be
mishandled in 32-bit-only readers (problem reported by Daniel
Fischer).

Changes to documentation

Distribute the SECURITY file (problem reported by Andreas Radke).


Release 2021b - 2021-09-24 16:23:00 -0700

Changes to maintenance procedure

The new file SECURITY covers how to report security-related bugs.

Several backward-compatibility links have been moved to the
'backward' file. These links, which range from Africa/Addis_Ababa
to Pacific/Saipan, are only for compatibility with now-obsolete
guidelines suggesting an entry for every ISO 3166 code.
The intercontinental convenience links Asia/Istanbul and
Europe/Nicosia have also been moved to 'backward'.

Changes to code

zic now creates each output file or link atomically,
possibly by creating a temporary file and then renaming it.
This avoids races where a TZ setting would temporarily stop
working while zic was installing a replacement file or link.

zic -L no longer omits the POSIX TZ string in its output.
Starting with 2020a, zic -L truncated its output according to the
"Expires" directive or "#expires" comment in the leapseconds file.
The resulting TZif files omitted daylight saving transitions after
the leap second table expired, which led to far less-accurate
predictions of times after the expiry. Although future timestamps
cannot be converted accurately in the presence of leap seconds, it
is more accurate to convert near-future timestamps with a few
seconds error than with an hour error, so zic -L no longer
truncates output in this way.

Instead, when zic -L is given the "Expires" directive, it now
outputs the expiration by appending a no-change entry to the leap
second table. Although this should work well with most TZif
readers, it does not conform to Internet RFC 8536 and some pickier
clients (including tzdb 2017c through 2021a) reject it, so
"Expires" directives are currently disabled by default. To enable
them, set the EXPIRES_LINE Makefile variable. If a TZif file uses
this new feature it is marked with a new TZif version number 4,
a format intended to be documented in a successor to RFC 8536.

zic -L LEAPFILE -r @LO no longer generates an invalid TZif file
that omits leap second information for the range LO..B when LO
falls between two leap seconds A and B. Instead, it generates a
TZif version 4 file that represents the previously-missing
information.

The TZif reader now allows the leap second table to begin with a
correction other than -1 or +1, and to contain adjacent
transitions with equal corrections. This supports TZif version 4.

The TZif reader now lets leap seconds occur less than 28 days
apart. This supports possible future TZif extensions.

Fix bug that caused 'localtime' etc. to crash when TZ was
set to a all-year DST string like "EST5EDT4,0/0,J365/25" that does
not conform to POSIX but does conform to Internet RFC 8536.

Fix another bug that caused 'localtime' etc. to crash when TZ was
set to a POSIX-conforming but unusual TZ string like
"EST5EDT4,0/0,J365/0", where almost all the year is DST.

Fix yet another bug that caused 'localtime' etc. to mishandle slim
TZif files containing leap seconds after the last explicit
transition in the table, or when handling far-future timestamps
in slim TZif files lacking leap seconds.

Fix localtime misbehavior involving positive leap seconds.
This change affects only behavior for "right" system time,
which contains leap seconds, and only if the UT offset is
not a multiple of 60 seconds when a positive leap second occurs.
(No such timezone exists in tzdb, luckily.) Without the fix,
the timestamp was ambiguous during a positive leap second.
With the fix, any seconds occurring after a positive leap second
and within the same localtime minute are counted through 60, not
through 59; their UT offset (tm_gmtoff) is the same as before.
Here is how the fix affects timestamps in a timezone with UT
offset +01:23:45 (5025 seconds) and with a positive leap second at
1972-06-30 23:59:60 UTC (78796800):

time_t without the fix with the fix
78796800 1972-07-01 01:23:45 1972-07-01 01:23:45 (leap second)
78796801 1972-07-01 01:23:45 1972-07-01 01:23:46
...
78796815 1972-07-01 01:23:59 1972-07-01 01:23:60
78796816 1972-07-01 01:24:00 1972-07-01 01:24:00

Fix an unlikely bug that caused 'localtime' etc. to misbehave if
civil time changes a few seconds before time_t wraps around, when
leap seconds are enabled.

Fix bug in zic -r; in some cases, the dummy time type after the
last time transition disagreed with the TZ string, contrary to
Internet RFC 8563 section 3.3.

Fix a bug with 'zic -r @X' when X is a negative leap second that
has a nonnegative correction. Without the fix, the output file
was truncated so that X appeared to be a positive leap second.
Fix a similar, even-less-likely bug when truncating at a positive
leap second that has a nonpositive correction.

zic -r now reports an error if given rolling leap seconds, as this
usage has never generally worked and is evidently unused.

zic now generates a POSIX-conforming TZ string for TZif files
where all-year DST is predicted for the indefinite future.
For example, for all-year Eastern Daylight Time, zic now generates
"XXX3EDT4,0/0,J365/23" where it previously generated
"EST5EDT,0/0,J365/25" or "". (Thanks to Michael Deckers for
noting the possibility of POSIX conformance.)

zic.c no longer requires sys/wait.h (thanks to spazmodius for
noting it wasn't needed).

When reading slim TZif files, zdump no longer mishandles leap
seconds on the rare platforms where time_t counts leap seconds,
fixing a bug introduced in 2014g.

zdump -v now outputs timestamps at boundaries of what localtime
and gmtime can represent, instead of the less-useful timestamps
one day after the minimum and one day before the maximum.
(Thanks to Arthur David Olson for prototype code, and to Manuela
Friedrich for debugging help.)

zdump's -c and -t options are now consistently inclusive for the
lower time bound and exclusive for the upper. Formerly they were
inconsistent. (Confusion noted by Martin Burnicki.)

Changes to build procedure

You can now compile with -DHAVE_MALLOC_ERRNO=0 to port to
non-POSIX hosts where malloc doesn't set errno.
(Problem reported by Jan Engelhardt.)

Changes to documentation

tzfile.5 better matches a draft successor to RFC 8536
<https://datatracker.ietf.org/doc/draft-murchison-rfc8536bis/01/>.

Merge tzcode-2021a
- No comments in the changelog about the code changes.

Merge tzcode2020b (except we keep tzsetwall(3) for now for compatibility,
and we were "slim" already)

Support for zic's long-obsolete '-y YEARISTYPE' option has been
removed and, with it, so has support for the TYPE field in Rule
lines, which is now reserved for compatibility with earlier zic.
These features were previously deprecated in release 2015f.
(Thanks to Tim Parenti.)

zic now defaults to '-b slim' instead of to '-b fat'.

zic's new '-l -' and '-p -' options uninstall any existing
localtime and posixrules files, respectively.

The undocumented and ineffective tzsetwall function has been
removed.

Bring in 2020a

Sync with 2019b:

zic's new -b option supports a way to control data bloat and to
test for year-2038 bugs in software that reads TZif files.
'zic -b fat' and 'zic -b slim' generate larger and smaller output;
for example, changing from fat to slim shrinks the Europe/London
file from 3648 to 1599 bytes, saving about 56%. Fat and slim
files represent the same set of timestamps and use the same TZif
format as documented in tzfile(5) and in Internet RFC 8536.
Fat format attempts to work around bugs or incompatibilities in
older software, notably software that mishandles 64-bit TZif data
or uses obsolete TZ strings like "EET-2EEST" that lack DST rules.
Slim format is more efficient and does not work around 64-bit bugs
or obsolete TZ strings. Currently zic defaults to fat format
unless you compile with -DZIC_BLOAT_DEFAULT=\"slim\"; this
out-of-the-box default is intended to change in future releases
as the buggy software often mishandles timestamps anyway.

zic no longer treats a set of rules ending in 2037 specially.
Previously, zic assumed that such a ruleset meant that future
timestamps could not be predicted, and therefore omitted a
POSIX-like TZ string in the TZif output. The old behavior is no
longer needed for current tzdata, and caused problems with newlib
when used with older tzdata (reported by David Gauchard).

zic no longer generates some artifact transitions. For example,
Europe/London no longer has a no-op transition in January 1996.

merge 2019a

Changes to code

zic now has an -r option to limit the time range of output data.
For example, 'zic -r @1000000000' limits the output data to
timestamps starting 1000000000 seconds after the Epoch.
This helps shrink output size and can be useful for applications
not needing the full timestamp history, such as TZDIST truncation;
see Internet RFC 8536 section 5.1. (Inspired by a feature request
from Christopher Wong, helped along by bug reports from Wong and
from Tim Parenti.)

Changes to documentation

Mention Internet RFC 8536 (February 2019), which documents TZif.

tz-link.html now cites tzdata-meta
<https://tzdata-meta.timtimeonline.com/>.

Welcome tzcode-2018g

Changes to code

When generating TZif files with leap seconds, zic no longer uses a
format that trips up older 32-bit clients, fixing a bug introduced
in 2018f. (Reported by Daniel Fischer.) Also, the zic workaround
for QTBUG-53071 now also works for TZif files with leap seconds.

The translator to rearguard format now rewrites the line
"Rule Japan 1948 1951 - Sep Sat>=8 25:00 0 S" to
"Rule Japan 1948 1951 - Sep Sun>=9 1:00 0 S".
This caters to zic before 2007 and to Oracle TZUpdater 2.2.0
and earlier. (Reported by Christos Zoulas.)

Changes to documentation

tzfile.5 has new sections on interoperability issues.

Update to 2018f:

Changes to code

zic now always generates TZif files where time type 0 is used for
timestamps before the first transition. This simplifies the
reading of TZif files and should not affect behavior of existing
TZif readers because the same set of time types is used; only
their internal indexes may have changed. This affects only the
legacy zones EST5EDT, CST6CDT, MST7MDT, PST8PDT, CET, MET, and
EET, which previously used nonzero types for these timestamps.

Because of the type 0 change, zic no longer outputs a dummy
transition at time -2**59 (before the Big Bang), as clients should
no longer need this to handle historical timestamps correctly.
This reverts a change introduced in 2013d and shrinks most TZif
files by a few bytes.

zic now supports negative time-of-day in Rule and Leap lines, e.g.,
"Rule X min max - Apr lastSun -6:00 1:00 -" means the transition
occurs at 18:00 on the Saturday before the last Sunday in April.
This behavior was documented in 2018a but the code did not
entirely match the documentation.

localtime.c no longer requires at least one time type in TZif
files that lack transitions or have a POSIX-style TZ string. This
future-proofs the code against possible future extensions to the
format that would allow TZif files with POSIX-style TZ strings and
without transitions or time types.

A read-access subscript error in localtime.c has been fixed.
It could occur only in TZif files with timecnt == 0, something that
does not happen in practice now but could happen in future versions.

localtime.c no longer ignores TZif POSIX-style TZ strings that
specify only standard time. Instead, these TZ strings now
override the default time type for timestamps after the last
transition (or for all time stamps if there are no transitions),
just as DST strings specifying DST have always done.

leapseconds.awk now outputs "#updated" and "#expires" comments,
and supports leap seconds at the ends of months other than June
and December. (Inspired by suggestions from Chris Woodbury.)

Changes to documentation

New restrictions: A Rule name must start with a character that
is neither an ASCII digit nor "-" nor "+", and an unquoted name
should not use characters in the set "!$%&'()*,/:;<=>?@[\]^`{|}~".
The latter restriction makes room for future extensions (a
possibility noted by Tom Lane).

tzfile.5 now documents what time types apply before the first and
after the last transition, if any.

Documentation now uses the spelling "timezone" for a TZ setting
that determines timestamp history, and "time zone" for a
geographic region currently sharing the same standard time.

The name "TZif" is now used for the tz binary data format.

tz-link.htm now mentions the A0 TimeZone Migration utilities.
(Thanks to Aldrin Martoq for the link.)

branches: 1.29.2;
Merge 2018e

Changes to code

zic now accepts subsecond precision in expressions like
00:19:32.13, which is approximately the legal time of the
Netherlands from 1835 to 1937. However, because it is
questionable whether the few recorded uses of non-integer offsets
had subsecond precision in practice, there are no plans for tzdata
to use this feature. (Thanks to Steve Allen for pointing out
the limitations of historical data in this area.)

The code is a bit more portable to MS-Windows. Installers can
compile with -DRESERVE_STD_EXT_IDS on MS-Windows platforms that
reserve identifiers like 'localtime'. (Thanks to Manuela
Friedrich).

Changes to documentation and commentary

theory.html now outlines tzdb's extensions to POSIX's model for
civil time, and has a section "POSIX features no longer needed"
that lists POSIX API components that are now vestigial.
(From suggestions by Steve Summit.) It also better distinguishes
time zones from tz regions. (From a suggestion by Guy Harris.)

Commentary is now more consistent about using the phrase "daylight
saving time", to match the C name tm_isdst. Daylight saving time
need not occur in summer, and need not have a positive offset from
standard time.

Commentary about historical transitions in Uruguay has been expanded
with links to many relevant legal documents.
(Thanks to Tim Parenti.)

Commentary now uses some non-ASCII characters with Unicode value
less than U+0100, as they can be useful and should work even with
older editors such as XEmacs.

branches: 1.28.2;
Merge tzcode2018c [ changelog with changes to tzdata sections removed ]

Release 2018c - 2018-01-22 23:00:44 -0800

Changes to build procedure

The build procedure now works around mawk 1.3.3's lack of support
for character class expressions. (Problem reported by Ohyama.)


Release 2018b - 2018-01-17 23:24:48 -0800

Changes to build procedure

The distribution now contains the file 'pacificnew' again.
This file was inadvertantly omitted in the 2018a distribution.
(Problem reported by Matias Fonzo.)


Release 2018a - 2018-01-12 22:29:21 -0800

Changes to build procedure

The default installation locations have been changed to mostly
match Debian circa 2017, instead of being designed as an add-on to
4.3BSD circa 1986. This affects the Makefile macros TOPDIR,
TZDIR, MANDIR, and LIBDIR. New Makefile macros TZDEFAULT, USRDIR,
USRSHAREDIR, BINDIR, ZDUMPDIR, and ZICDIR let installers tailor
locations more precisely. (This responds to suggestions from
Brian Inglis and from Steve Summit.)

The default installation procedure no longer creates the
backward-compatibility link US/Pacific-New, which causes
confusion during user setup (e.g., see Debian bug 815200).
Use 'make BACKWARD="backward pacificnew"' to create the link
anyway, for now. Eventually we plan to remove the link entirely.

tzdata.zi now contains a version-number comment.
(Suggested by Tom Lane.)

The Makefile now quotes values like BACKWARD more carefully when
passing them to the shell. (Problem reported by Zefram.)

Builders no longer need to specify -DHAVE_SNPRINTF on platforms
that have snprintf and use pre-C99 compilers. (Problem reported
by Jon Skeet.)

Changes to code

zic has a new option -t FILE that specifies the location of the
file that determines local time when TZ is unset. The default for
this location can be configured via the new TZDEFAULT makefile
macro, which defaults to /etc/localtime.

Diagnostics and commentary now distinguish UT from UTC more
carefully; see theory.html for more information about UT vs UTC.

zic has been ported to GCC 8's -Wstringop-truncation option.
(Problem reported by Martin Sebor.)

Changes to documentation and commentary

The zic man page now documents the longstanding behavior that
times and years can be out of the usual range, with negative times
counting backwards from midnight and with year 0 preceding year 1.
(Problem reported by Michael Deckers.)

The theory.html file now mentions the POSIX limit of six chars
per abbreviation, and lists alphabetic abbreviations used.

The files tz-art.htm and tz-link.htm have been renamed to
tz-art.html and tz-link.html, respectively, for consistency with
other file names and to simplify web server configuration.

Welcome to 2017c:

zic and the reference runtime now reject multiple leap seconds
within 28 days of each other, or leap seconds before the Epoch.
As a result, support for double leap seconds, which was
obsolescent and undocumented, has been removed. Double leap
seconds were an error in the C89 standard; they have never existed
in civil timekeeping. (Thanks to Robert Elz and Bradley White for
noticing glitches in the code that uncovered this problem.)

zic now warns about use of the obsolescent and undocumented -y
option, and about use of the obsolescent TYPE field of Rule lines.

zic now allows unambiguous abbreviations like "Sa" and "Su" for
weekdays; formerly it rejected them due to a bug. Conversely, zic
no longer considers non-prefixes to be abbreviations; for example,
it no longer accepts "lF" as an abbreviation for "lastFriday".
Also, zic warns about the undocumented usage with a "last-"
prefix, e.g., "last-Fri".

Similarly, zic now accepts the unambiguous abbreviation "L" for
"Link" in ordinary context and for "Leap" in leap-second context.
Conversely, zic no longer accepts non-prefixes such as "La" as
abbreviations for words like "Leap".

zic no longer accepts leap second lines in ordinary input, or
ordinary lines in leap second input. Formerly, zic sometimes
warned about this undocumented usage and handled it incorrectly.

The new macro HAVE_TZNAME governs whether the tzname external
variable is exported, instead of USG_COMPAT. USG_COMPAT now
governs only the external variables "timezone" and "daylight".
This change is needed because the three variables are not in the
same category: although POSIX requires tzname, it specifies the
other two variables as optional. Also, USG_COMPAT is now 1 or 0:
if not defined, the code attempts to guess it from other macros.

localtime.c and difftime.c no longer require stdio.h, and .c files
other than zic.c no longer require sys/wait.h.

zdump.c no longer assumes snprintf. (Reported by Jonathan Leffler.)

Calculation of time_t extrema works around a bug in GCC 4.8.4
(Reported by Stan Shebs and Joseph Myers.)

zic.c no longer mistranslates formats of line numbers in non-English
locales. (Problem reported by Benno Schulenberg.)

Several minor changes have been made to the code to make it a
bit easier to port to MS-Windows and Solaris. (Thanks to Kees
Dekker for reporting the problems.)

Changes to documentation and commentary

The two new files 'theory.html' and 'calendars' contain the
contents of the removed file 'Theory'. The goal is to document
tzdb theory more accessibly.

The zic man page now documents abbreviation rules.

tz-link.htm now covers how to apply tzdata changes to clients.
(Thanks to Jorge F��bregas for the AIX link.) It also mentions MySQL.

The leap-seconds.list URL has been updated to something that is
more reliable for tzdb. (Thanks to Tim Parenti and Brian Inglis.)

merge 2015f

merge tzcode2015e:

Changes affecting code

When displaying data, tzselect converts it to the current locale's
encoding if the iconv command works. (Problem reported by random832.)

tzselect no longer mishandles Dominica, fixing a bug introduced
in Release 2014f. (Problem reported by Owen Leibman.)

zic -l no longer fails when compiled with -DTZDEFAULT=\"/etc/localtime\".
This fixes a bug introduced in Release 2014f.
(Problem reported by Leonardo Chiquitto.)

Sync with tzcode2014h

merge tzcode2014f via patch

branches: 1.22.2;
welcome to 2014d; zic big bang fixes:
some programs did not handle large negative time_t values well (gnome)

branches: 1.21.2;
Welcome to tzcode 2013e:

Changes affecting API

The 'zic' command now outputs a dummy transition when far-future
data can't be summarized using a TZ string, and uses a 402-year
window rather than a 400-year window. For the current data, this
affects only the Asia/Tehran file. It does not affect any of the
time stamps that this file represents, so zdump outputs the same
information as before. (Thanks to Andrew Main (Zefram).)

The 'date' command has a new '-r' option, which lets you specify
the integer time to display, a la FreeBSD.

The 'tzselect' command has two new options '-c' and '-n', which lets you
select a zone based on latitude and longitude.

The 'zic' command's '-v' option now warns about constructs that
require the new version-3 binary file format. (Thanks to Arthur
David Olson for the suggestion.)

Support for floating-point time_t has been removed.
It was always dicey, and POSIX no longer requires it.
(Thanks to Eric Blake for suggesting to the POSIX committee to
remove it, and thanks to Alan Barrett, Clive D.W. Feather, Andy
Heninger, Arthur David Olson, and Alois Treindl, for reporting
bugs and elucidating some of the corners of the old floating-point
implementation.)

The signatures of 'offtime', 'timeoff', and 'gtime' have been
changed back to the old practice of using 'long' to represent UT
offsets. This had been inadvertently and mistakenly changed to
'int_fast32_t'. (Thanks to Christos Zoulos.)

The code avoids undefined behavior on integer overflow in some
more places, including gmtime, localtime, mktime and zdump.

Changes affecting the zdump utility

zdump now outputs "UT" when referring to Universal Time, not "UTC".
"UTC" does not make sense for time stamps that predate the introduction
of UTC, whereas "UT", a more-generic term, does. (Thanks to Steve Allen
for clarifying UT vs UTC.)

Data changes affecting behavior of tzselect and similar programs

Country code BQ is now called the more-common name "Caribbean Netherlands"
rather than the more-official "Bonaire, St Eustatius & Saba".

Remove from zone.tab the names America/Montreal, America/Shiprock,
and Antarctica/South_Pole, as they are equivalent to existing
same-country-code zones for post-1970 time stamps. The data for
these names are unchanged, so the names continue to work as before.

Changes affecting code internals

zic -c now runs way faster on 64-bit hosts when given large numbers.

zic now uses vfprintf to avoid allocating and freeing some memory.

tzselect now computes the list of continents from the data,
rather than have it hard-coded.

Minor changes pacify GCC 4.7.3 and GCC 4.8.1.

Changes affecting the build procedure

The 'leapseconds' file is now generated automatically from a
new file 'leap-seconds.list', which is a copy of
<ftp://time.nist.gov/pub/leap-seconds.list>.
A new source file 'leapseconds.awk' implements this.
The goal is simplification of the future maintenance of 'leapseconds'.

When building the 'posix' or 'right' subdirectories, if the
subdirectory would be a copy of the default subdirectory, it is
now made a symbolic link if that is supported. This saves about
2 MB of file system space.

The links America/Shiprock and Antarctica/South_Pole have been
moved to the 'backward' file. This affects only nondefault builds
that omit 'backward'.

Changes affecting documentation and commentary

Changes to the 'tzfile' man page

It now mentions that the binary file format may be extended in
future versions by appending data.

It now refers to the 'zdump' and 'zic' man pages.

Changes to the 'zic' man page

It lists conditions that elicit a warning with '-v'.

It says that the behavior is unspecified when duplicate names
are given, or if the source of one link is the target of another.

Its examples are updated to match the latest data.

The definition of white space has been clarified slightly.
(Thanks to Michael Deckers.)

Changes to the 'Theory' file

There is a new section about the accuracy of the tz database,
describing the many ways that errors can creep in, and
explaining why so many of the pre-1970 time stamps are wrong or
misleading (thanks to Steve Allen, Lester Caine, and Garrett
Wollman for discussions that contributed to this).

The 'Theory' file describes LMT better (this follows a
suggestion by Guy Harris).

It refers to the 2013 edition of POSIX rather than the 2004 edition.

It's mentioned that excluding 'backward' should not affect the
other data, and it suggests at least one zone.tab name per
inhabited country (thanks to Stephen Colebourne).

Some longstanding restrictions on names are documented, e.g.,
'America/New_York' precludes 'America/New_York/Bronx'.

It gives more reasons for the 1970 cutoff.

It now mentions which time_t variants are supported, such as
signed integer time_t. (Thanks to Paul Goyette for reporting
typos in an experimental version of this change.)

(Thanks to Philip Newton for correcting typos in these changes.)

Documentation and commentary is more careful to distinguish UT in
general from UTC in particular. (Thanks to Steve Allen.)

Add a better source for the Zurich 1894 transition.
(Thanks to Pierre-Yves Berger.)

Update shapefile citations in tz-link.htm. (Thanks to Guy Harris.)

branches: 1.20.2;
merge 2012e

branches: 1.19.2;
bring in the 2011i changes.

New sentence, new line.

Fix up mix of man(7)/mdoc(7).

Import tzcode2009k.
- now understands 64bit time_t and 64bit data in timezone files.
- localtime(), gmtime(), asctime() and ctime() may now fail with
a NULL result if time_t cannot be represented by struct tm.

Fix preamble to match order set out by mdoc(7). Discussed with wiz.

branches: 1.14.42;
Merge tzcode2003e.

Merge tzcode2003d.

Use a better width argument.

Generate <>& symbolically. I'm avoiding .../dist/... directories for now.

mdoc'ify

branches: 1.9.6;
Merge tzcode1999i.

branches: 1.8.6;
Merge tzcode1998h.

sync with tzcode1998a

Sync with tzcode1997e

alternate -> alternative, per PR 2643

sync with tzcode96a

/usr/local/etc/zoneinfo -> /usr/share/zoneinfo; PR #1398

branches: 1.2.2;
Added NetBSD Id.
Removed "new" from newctime(3) references.

branches: 1.1.1;
Initial revision

Update tzcode from 2022g to 2023c:

Release 2023c - 2023-03-28 12:42:14 -0700

Release 2023b - 2023-03-23 19:50:38 -0700

Release 2023a - 2023-03-22 12:39:33 -0700

Changes to code

You can now tell tzselect local time, to simplify later choices.
Select the 'time' option in its first prompt.

You can now compile with -DTZNAME_MAXIMUM=N to limit time zone
abbreviations to N bytes (default 255). The reference runtime
library now rejects POSIX-style TZ strings that contain longer
abbreviations, treating them as UTC. Previously the limit was
platform dependent and abbreviations were silently truncated to
16 bytes even when the limit was greater than 16.

The code by default is now designed for C99 or later. To build in
a C89 environment, compile with -DPORT_TO_C89. To support C89
callers of the tzcode library, compile with -DSUPPORT_C89. The
two new macros are transitional aids planned to be removed in a
future version, when C99 or later will be required.

The code now builds again on pre-C99 platforms, if you compile
with -DPORT_TO_C89. This fixes a bug introduced in 2022f.

On C23-compatible platforms tzcode no longer uses syntax like
'static [[noreturn]] void usage(void);'. Instead, it uses
'[[noreturn]] static void usage(void);' as strict C23 requires.
(Problem reported by Houge Langley.)

The code's functions now constrain their arguments with the C
'restrict' keyword consistently with their documentation.
This may allow future optimizations.

zdump again builds standalone with ckdadd and without setenv,
fixing a bug introduced in 2022g. (Problem reported by panic.)

leapseconds.awk can now process a leap seconds file that never
expires; this might be useful if leap seconds are discontinued.

Changes to commentary

tz-link.html has a new section "Coordinating with governments and
distributors". (Thanks to Neil Fuller for some of the text.)

To improve tzselect diagnostics, zone1970.tab's comments column is
now limited to countries that have multiple timezones.

Note that leap seconds are planned to be discontinued by 2035.

Fix formatting corruption for manpages from tzcode.

Comment out .TH macros, that cause mandoc(1) to run into man(7) mode.

Merge in 2022g:

Although tzcode still works with C89, bugs found in recent routine
maintenance indicate that bitrot has set in and that in practice
C89 is no longer used to build tzcode. As it is a maintenance
burden, support for C89 is planned to be removed soon. Instead,
please use compilers compatible with C99, C11, C17, or C23.

timegm, which tzcode implemented in 1989, will finally be
standardized 34 years later as part of C23, so timegm is now
supported even if STD_INSPIRED is not defined.

Fix bug in zdump's tzalloc emulation on hosts that lack tm_zone.
(Problem reported by ��o��n Tr���n C��ng Danh.)

Fix bug in zic on hosts where malloc(0) yields NULL on success.
(Problem reported by Tim McBrayer for AIX 6.1.)

Fix zic configuration to avoid linkage failures on some platforms.
(Problems reported by Gilmore Davidson and Igor Ivanov.)

Work around MS-Windows nmake incompatibility with POSIX.
(Problem reported by Manuela Friedrich.)

Port mktime and strftime to debugging platforms where accessing
uninitialized data has undefined behavior (strftime problem
reported by Robert Elz).

Check more carefully for unlikely integer overflows, preferring
C23 <stdckdint.h> to overflow checking by hand, as the latter has
had obscure bugs.

Update to tzcode2022f

Changes to code

zic now supports links to links regardless of input line order.
For example, if Australia/Sydney is a Zone, the lines
Link Australia/Canberra Australia/ACT
Link Australia/Sydney Australia/Canberra
now work correctly, even though the shell commands
ln Australia/Canberra Australia/ACT
ln Australia/Sydney Australia/Canberra
would fail because the first command attempts to use a link
Australia/Canberra that does not exist until after the second
command is executed. Previously, zic had unspecified behavior if
a Link line's target was another link, and zic often misbehaved if
a Link line's target was a later Link line.

Fix line number in zic's diagnostic for a link to a link.

Fix a bug that caused localtime to mishandle timestamps starting
in the year 2438 when reading data generated by 'zic -b fat' when
distant-future DST transitions occur at times given in standard
time or in UT, not the usual case of local time. This occurs when
the corresponding .zi Rule lines specify DST transitions with TO
columns of 'max' and AT columns that end in 's' or 'u'. The
number 2438 comes from the 32-bit limit in the year 2038, plus the
400-year Gregorian cycle. (Problem reported by Bradley White.)

On glibc 2.34 and later, which optionally supports 64-bit time_t
on platforms like x86 where time_t was traditionally 32 bits,
default time_t to 64 instead of 32 bits. This lets functions like
localtime support timestamps after the year 2038, and fixes
year-2038 problems in zic when accessing files dated after 2038.
To continue to limit time_t to 32 bits on these platforms, use
"make CFLAGS='-D_TIME_BITS=32'".

In C code, do not enable large-file support on platforms like AIX
and macOS that no longer need it now that tzcode does not use
off_t or related functions like 'stat'. Large-file support is
still enabled by default on GNU/Linux, as it is needed for 64-bit
time_t support.

In C code, prefer C23 keywords to pre-C23 macros for alignof,
bool, false, and true. Also, use the following C23 features if
available: __has_include, unreachable.

zic no longer works around Qt bug 53071, as the relevant Qt
releases have been out of support since 2019. This change affects
only fat TZif files, as thin files never had the workaround.

zdump no longer modifies the environ vector when compiled on
platforms lacking tm_zone or when compiled with -DUSE_LTZ=0.
This avoid undefined behavior on POSIX platforms.

add missing text.

Welcome to 2022b:

zic has a new option '-R @N' to output explicit transitions < N.
(Need suggested by Almaz Mingaleev.)

'zic -r @N' no longer outputs bad data when N < first transition.
(Problem introduced in 2021d and reported by Peter Krefting.)

zic now checks its input for NUL bytes and unterminated lines, and
now supports input line lengths up to 2048 (not 512) bytes.

gmtime and related code now use the abbreviation "UTC" not "GMT".
POSIX is being revised to require this.

When tzset and related functions set vestigial static variables
like tzname, they now prefer specified timestamps to unspecified ones.
(Problem reported by Almaz Mingaleev.)

zic no longer complains "can't determine time zone abbreviation to
use just after until time" when a transition to a new standard
time occurs simultanously with the first DST fallback transition.

Change to code and documentation from 2021a -> 2021e

Release 2021e - 2021-10-21 18:41:00 -0700

Changes to code

none


Release 2021d - 2021-10-15 13:48:18 -0700

Changes to code

'zic -r' now uses "-00" time zone abbreviations for intervals
with UT offsets that are unspecified due to -r truncation.
This implements a change in draft Internet RFC 8536bis.


Release 2021c - 2021-10-01 14:21:49 -0700

Changes to code

Fix a bug in 'zic -b fat' that caused old timestamps to be
mishandled in 32-bit-only readers (problem reported by Daniel
Fischer).

Changes to documentation

Distribute the SECURITY file (problem reported by Andreas Radke).


Release 2021b - 2021-09-24 16:23:00 -0700

Changes to maintenance procedure

The new file SECURITY covers how to report security-related bugs.

Several backward-compatibility links have been moved to the
'backward' file. These links, which range from Africa/Addis_Ababa
to Pacific/Saipan, are only for compatibility with now-obsolete
guidelines suggesting an entry for every ISO 3166 code.
The intercontinental convenience links Asia/Istanbul and
Europe/Nicosia have also been moved to 'backward'.

Changes to code

zic now creates each output file or link atomically,
possibly by creating a temporary file and then renaming it.
This avoids races where a TZ setting would temporarily stop
working while zic was installing a replacement file or link.

zic -L no longer omits the POSIX TZ string in its output.
Starting with 2020a, zic -L truncated its output according to the
"Expires" directive or "#expires" comment in the leapseconds file.
The resulting TZif files omitted daylight saving transitions after
the leap second table expired, which led to far less-accurate
predictions of times after the expiry. Although future timestamps
cannot be converted accurately in the presence of leap seconds, it
is more accurate to convert near-future timestamps with a few
seconds error than with an hour error, so zic -L no longer
truncates output in this way.

Instead, when zic -L is given the "Expires" directive, it now
outputs the expiration by appending a no-change entry to the leap
second table. Although this should work well with most TZif
readers, it does not conform to Internet RFC 8536 and some pickier
clients (including tzdb 2017c through 2021a) reject it, so
"Expires" directives are currently disabled by default. To enable
them, set the EXPIRES_LINE Makefile variable. If a TZif file uses
this new feature it is marked with a new TZif version number 4,
a format intended to be documented in a successor to RFC 8536.

zic -L LEAPFILE -r @LO no longer generates an invalid TZif file
that omits leap second information for the range LO..B when LO
falls between two leap seconds A and B. Instead, it generates a
TZif version 4 file that represents the previously-missing
information.

The TZif reader now allows the leap second table to begin with a
correction other than -1 or +1, and to contain adjacent
transitions with equal corrections. This supports TZif version 4.

The TZif reader now lets leap seconds occur less than 28 days
apart. This supports possible future TZif extensions.

Fix bug that caused 'localtime' etc. to crash when TZ was
set to a all-year DST string like "EST5EDT4,0/0,J365/25" that does
not conform to POSIX but does conform to Internet RFC 8536.

Fix another bug that caused 'localtime' etc. to crash when TZ was
set to a POSIX-conforming but unusual TZ string like
"EST5EDT4,0/0,J365/0", where almost all the year is DST.

Fix yet another bug that caused 'localtime' etc. to mishandle slim
TZif files containing leap seconds after the last explicit
transition in the table, or when handling far-future timestamps
in slim TZif files lacking leap seconds.

Fix localtime misbehavior involving positive leap seconds.
This change affects only behavior for "right" system time,
which contains leap seconds, and only if the UT offset is
not a multiple of 60 seconds when a positive leap second occurs.
(No such timezone exists in tzdb, luckily.) Without the fix,
the timestamp was ambiguous during a positive leap second.
With the fix, any seconds occurring after a positive leap second
and within the same localtime minute are counted through 60, not
through 59; their UT offset (tm_gmtoff) is the same as before.
Here is how the fix affects timestamps in a timezone with UT
offset +01:23:45 (5025 seconds) and with a positive leap second at
1972-06-30 23:59:60 UTC (78796800):

time_t without the fix with the fix
78796800 1972-07-01 01:23:45 1972-07-01 01:23:45 (leap second)
78796801 1972-07-01 01:23:45 1972-07-01 01:23:46
...
78796815 1972-07-01 01:23:59 1972-07-01 01:23:60
78796816 1972-07-01 01:24:00 1972-07-01 01:24:00

Fix an unlikely bug that caused 'localtime' etc. to misbehave if
civil time changes a few seconds before time_t wraps around, when
leap seconds are enabled.

Fix bug in zic -r; in some cases, the dummy time type after the
last time transition disagreed with the TZ string, contrary to
Internet RFC 8563 section 3.3.

Fix a bug with 'zic -r @X' when X is a negative leap second that
has a nonnegative correction. Without the fix, the output file
was truncated so that X appeared to be a positive leap second.
Fix a similar, even-less-likely bug when truncating at a positive
leap second that has a nonpositive correction.

zic -r now reports an error if given rolling leap seconds, as this
usage has never generally worked and is evidently unused.

zic now generates a POSIX-conforming TZ string for TZif files
where all-year DST is predicted for the indefinite future.
For example, for all-year Eastern Daylight Time, zic now generates
"XXX3EDT4,0/0,J365/23" where it previously generated
"EST5EDT,0/0,J365/25" or "". (Thanks to Michael Deckers for
noting the possibility of POSIX conformance.)

zic.c no longer requires sys/wait.h (thanks to spazmodius for
noting it wasn't needed).

When reading slim TZif files, zdump no longer mishandles leap
seconds on the rare platforms where time_t counts leap seconds,
fixing a bug introduced in 2014g.

zdump -v now outputs timestamps at boundaries of what localtime
and gmtime can represent, instead of the less-useful timestamps
one day after the minimum and one day before the maximum.
(Thanks to Arthur David Olson for prototype code, and to Manuela
Friedrich for debugging help.)

zdump's -c and -t options are now consistently inclusive for the
lower time bound and exclusive for the upper. Formerly they were
inconsistent. (Confusion noted by Martin Burnicki.)

Changes to build procedure

You can now compile with -DHAVE_MALLOC_ERRNO=0 to port to
non-POSIX hosts where malloc doesn't set errno.
(Problem reported by Jan Engelhardt.)

Changes to documentation

tzfile.5 better matches a draft successor to RFC 8536
<https://datatracker.ietf.org/doc/draft-murchison-rfc8536bis/01/>.

Merge tzcode-2021a
- No comments in the changelog about the code changes.

Merge tzcode2020b (except we keep tzsetwall(3) for now for compatibility,
and we were "slim" already)

Support for zic's long-obsolete '-y YEARISTYPE' option has been
removed and, with it, so has support for the TYPE field in Rule
lines, which is now reserved for compatibility with earlier zic.
These features were previously deprecated in release 2015f.
(Thanks to Tim Parenti.)

zic now defaults to '-b slim' instead of to '-b fat'.

zic's new '-l -' and '-p -' options uninstall any existing
localtime and posixrules files, respectively.

The undocumented and ineffective tzsetwall function has been
removed.

Bring in 2020a

Sync with 2019b:

zic's new -b option supports a way to control data bloat and to
test for year-2038 bugs in software that reads TZif files.
'zic -b fat' and 'zic -b slim' generate larger and smaller output;
for example, changing from fat to slim shrinks the Europe/London
file from 3648 to 1599 bytes, saving about 56%. Fat and slim
files represent the same set of timestamps and use the same TZif
format as documented in tzfile(5) and in Internet RFC 8536.
Fat format attempts to work around bugs or incompatibilities in
older software, notably software that mishandles 64-bit TZif data
or uses obsolete TZ strings like "EET-2EEST" that lack DST rules.
Slim format is more efficient and does not work around 64-bit bugs
or obsolete TZ strings. Currently zic defaults to fat format
unless you compile with -DZIC_BLOAT_DEFAULT=\"slim\"; this
out-of-the-box default is intended to change in future releases
as the buggy software often mishandles timestamps anyway.

zic no longer treats a set of rules ending in 2037 specially.
Previously, zic assumed that such a ruleset meant that future
timestamps could not be predicted, and therefore omitted a
POSIX-like TZ string in the TZif output. The old behavior is no
longer needed for current tzdata, and caused problems with newlib
when used with older tzdata (reported by David Gauchard).

zic no longer generates some artifact transitions. For example,
Europe/London no longer has a no-op transition in January 1996.

merge 2019a

Changes to code

zic now has an -r option to limit the time range of output data.
For example, 'zic -r @1000000000' limits the output data to
timestamps starting 1000000000 seconds after the Epoch.
This helps shrink output size and can be useful for applications
not needing the full timestamp history, such as TZDIST truncation;
see Internet RFC 8536 section 5.1. (Inspired by a feature request
from Christopher Wong, helped along by bug reports from Wong and
from Tim Parenti.)

Changes to documentation

Mention Internet RFC 8536 (February 2019), which documents TZif.

tz-link.html now cites tzdata-meta
<https://tzdata-meta.timtimeonline.com/>.

Welcome tzcode-2018g

Changes to code

When generating TZif files with leap seconds, zic no longer uses a
format that trips up older 32-bit clients, fixing a bug introduced
in 2018f. (Reported by Daniel Fischer.) Also, the zic workaround
for QTBUG-53071 now also works for TZif files with leap seconds.

The translator to rearguard format now rewrites the line
"Rule Japan 1948 1951 - Sep Sat>=8 25:00 0 S" to
"Rule Japan 1948 1951 - Sep Sun>=9 1:00 0 S".
This caters to zic before 2007 and to Oracle TZUpdater 2.2.0
and earlier. (Reported by Christos Zoulas.)

Changes to documentation

tzfile.5 has new sections on interoperability issues.

Update to 2018f:

Changes to code

zic now always generates TZif files where time type 0 is used for
timestamps before the first transition. This simplifies the
reading of TZif files and should not affect behavior of existing
TZif readers because the same set of time types is used; only
their internal indexes may have changed. This affects only the
legacy zones EST5EDT, CST6CDT, MST7MDT, PST8PDT, CET, MET, and
EET, which previously used nonzero types for these timestamps.

Because of the type 0 change, zic no longer outputs a dummy
transition at time -2**59 (before the Big Bang), as clients should
no longer need this to handle historical timestamps correctly.
This reverts a change introduced in 2013d and shrinks most TZif
files by a few bytes.

zic now supports negative time-of-day in Rule and Leap lines, e.g.,
"Rule X min max - Apr lastSun -6:00 1:00 -" means the transition
occurs at 18:00 on the Saturday before the last Sunday in April.
This behavior was documented in 2018a but the code did not
entirely match the documentation.

localtime.c no longer requires at least one time type in TZif
files that lack transitions or have a POSIX-style TZ string. This
future-proofs the code against possible future extensions to the
format that would allow TZif files with POSIX-style TZ strings and
without transitions or time types.

A read-access subscript error in localtime.c has been fixed.
It could occur only in TZif files with timecnt == 0, something that
does not happen in practice now but could happen in future versions.

localtime.c no longer ignores TZif POSIX-style TZ strings that
specify only standard time. Instead, these TZ strings now
override the default time type for timestamps after the last
transition (or for all time stamps if there are no transitions),
just as DST strings specifying DST have always done.

leapseconds.awk now outputs "#updated" and "#expires" comments,
and supports leap seconds at the ends of months other than June
and December. (Inspired by suggestions from Chris Woodbury.)

Changes to documentation

New restrictions: A Rule name must start with a character that
is neither an ASCII digit nor "-" nor "+", and an unquoted name
should not use characters in the set "!$%&'()*,/:;<=>?@[\]^`{|}~".
The latter restriction makes room for future extensions (a
possibility noted by Tom Lane).

tzfile.5 now documents what time types apply before the first and
after the last transition, if any.

Documentation now uses the spelling "timezone" for a TZ setting
that determines timestamp history, and "time zone" for a
geographic region currently sharing the same standard time.

The name "TZif" is now used for the tz binary data format.

tz-link.htm now mentions the A0 TimeZone Migration utilities.
(Thanks to Aldrin Martoq for the link.)

branches: 1.29.2;
Merge 2018e

Changes to code

zic now accepts subsecond precision in expressions like
00:19:32.13, which is approximately the legal time of the
Netherlands from 1835 to 1937. However, because it is
questionable whether the few recorded uses of non-integer offsets
had subsecond precision in practice, there are no plans for tzdata
to use this feature. (Thanks to Steve Allen for pointing out
the limitations of historical data in this area.)

The code is a bit more portable to MS-Windows. Installers can
compile with -DRESERVE_STD_EXT_IDS on MS-Windows platforms that
reserve identifiers like 'localtime'. (Thanks to Manuela
Friedrich).

Changes to documentation and commentary

theory.html now outlines tzdb's extensions to POSIX's model for
civil time, and has a section "POSIX features no longer needed"
that lists POSIX API components that are now vestigial.
(From suggestions by Steve Summit.) It also better distinguishes
time zones from tz regions. (From a suggestion by Guy Harris.)

Commentary is now more consistent about using the phrase "daylight
saving time", to match the C name tm_isdst. Daylight saving time
need not occur in summer, and need not have a positive offset from
standard time.

Commentary about historical transitions in Uruguay has been expanded
with links to many relevant legal documents.
(Thanks to Tim Parenti.)

Commentary now uses some non-ASCII characters with Unicode value
less than U+0100, as they can be useful and should work even with
older editors such as XEmacs.

branches: 1.28.2;
Merge tzcode2018c [ changelog with changes to tzdata sections removed ]

Release 2018c - 2018-01-22 23:00:44 -0800

Changes to build procedure

The build procedure now works around mawk 1.3.3's lack of support
for character class expressions. (Problem reported by Ohyama.)


Release 2018b - 2018-01-17 23:24:48 -0800

Changes to build procedure

The distribution now contains the file 'pacificnew' again.
This file was inadvertantly omitted in the 2018a distribution.
(Problem reported by Matias Fonzo.)


Release 2018a - 2018-01-12 22:29:21 -0800

Changes to build procedure

The default installation locations have been changed to mostly
match Debian circa 2017, instead of being designed as an add-on to
4.3BSD circa 1986. This affects the Makefile macros TOPDIR,
TZDIR, MANDIR, and LIBDIR. New Makefile macros TZDEFAULT, USRDIR,
USRSHAREDIR, BINDIR, ZDUMPDIR, and ZICDIR let installers tailor
locations more precisely. (This responds to suggestions from
Brian Inglis and from Steve Summit.)

The default installation procedure no longer creates the
backward-compatibility link US/Pacific-New, which causes
confusion during user setup (e.g., see Debian bug 815200).
Use 'make BACKWARD="backward pacificnew"' to create the link
anyway, for now. Eventually we plan to remove the link entirely.

tzdata.zi now contains a version-number comment.
(Suggested by Tom Lane.)

The Makefile now quotes values like BACKWARD more carefully when
passing them to the shell. (Problem reported by Zefram.)

Builders no longer need to specify -DHAVE_SNPRINTF on platforms
that have snprintf and use pre-C99 compilers. (Problem reported
by Jon Skeet.)

Changes to code

zic has a new option -t FILE that specifies the location of the
file that determines local time when TZ is unset. The default for
this location can be configured via the new TZDEFAULT makefile
macro, which defaults to /etc/localtime.

Diagnostics and commentary now distinguish UT from UTC more
carefully; see theory.html for more information about UT vs UTC.

zic has been ported to GCC 8's -Wstringop-truncation option.
(Problem reported by Martin Sebor.)

Changes to documentation and commentary

The zic man page now documents the longstanding behavior that
times and years can be out of the usual range, with negative times
counting backwards from midnight and with year 0 preceding year 1.
(Problem reported by Michael Deckers.)

The theory.html file now mentions the POSIX limit of six chars
per abbreviation, and lists alphabetic abbreviations used.

The files tz-art.htm and tz-link.htm have been renamed to
tz-art.html and tz-link.html, respectively, for consistency with
other file names and to simplify web server configuration.

Welcome to 2017c:

zic and the reference runtime now reject multiple leap seconds
within 28 days of each other, or leap seconds before the Epoch.
As a result, support for double leap seconds, which was
obsolescent and undocumented, has been removed. Double leap
seconds were an error in the C89 standard; they have never existed
in civil timekeeping. (Thanks to Robert Elz and Bradley White for
noticing glitches in the code that uncovered this problem.)

zic now warns about use of the obsolescent and undocumented -y
option, and about use of the obsolescent TYPE field of Rule lines.

zic now allows unambiguous abbreviations like "Sa" and "Su" for
weekdays; formerly it rejected them due to a bug. Conversely, zic
no longer considers non-prefixes to be abbreviations; for example,
it no longer accepts "lF" as an abbreviation for "lastFriday".
Also, zic warns about the undocumented usage with a "last-"
prefix, e.g., "last-Fri".

Similarly, zic now accepts the unambiguous abbreviation "L" for
"Link" in ordinary context and for "Leap" in leap-second context.
Conversely, zic no longer accepts non-prefixes such as "La" as
abbreviations for words like "Leap".

zic no longer accepts leap second lines in ordinary input, or
ordinary lines in leap second input. Formerly, zic sometimes
warned about this undocumented usage and handled it incorrectly.

The new macro HAVE_TZNAME governs whether the tzname external
variable is exported, instead of USG_COMPAT. USG_COMPAT now
governs only the external variables "timezone" and "daylight".
This change is needed because the three variables are not in the
same category: although POSIX requires tzname, it specifies the
other two variables as optional. Also, USG_COMPAT is now 1 or 0:
if not defined, the code attempts to guess it from other macros.

localtime.c and difftime.c no longer require stdio.h, and .c files
other than zic.c no longer require sys/wait.h.

zdump.c no longer assumes snprintf. (Reported by Jonathan Leffler.)

Calculation of time_t extrema works around a bug in GCC 4.8.4
(Reported by Stan Shebs and Joseph Myers.)

zic.c no longer mistranslates formats of line numbers in non-English
locales. (Problem reported by Benno Schulenberg.)

Several minor changes have been made to the code to make it a
bit easier to port to MS-Windows and Solaris. (Thanks to Kees
Dekker for reporting the problems.)

Changes to documentation and commentary

The two new files 'theory.html' and 'calendars' contain the
contents of the removed file 'Theory'. The goal is to document
tzdb theory more accessibly.

The zic man page now documents abbreviation rules.

tz-link.htm now covers how to apply tzdata changes to clients.
(Thanks to Jorge F��bregas for the AIX link.) It also mentions MySQL.

The leap-seconds.list URL has been updated to something that is
more reliable for tzdb. (Thanks to Tim Parenti and Brian Inglis.)

merge 2015f

merge tzcode2015e:

Changes affecting code

When displaying data, tzselect converts it to the current locale's
encoding if the iconv command works. (Problem reported by random832.)

tzselect no longer mishandles Dominica, fixing a bug introduced
in Release 2014f. (Problem reported by Owen Leibman.)

zic -l no longer fails when compiled with -DTZDEFAULT=\"/etc/localtime\".
This fixes a bug introduced in Release 2014f.
(Problem reported by Leonardo Chiquitto.)

Sync with tzcode2014h

merge tzcode2014f via patch

branches: 1.22.2;
welcome to 2014d; zic big bang fixes:
some programs did not handle large negative time_t values well (gnome)

branches: 1.21.2;
Welcome to tzcode 2013e:

Changes affecting API

The 'zic' command now outputs a dummy transition when far-future
data can't be summarized using a TZ string, and uses a 402-year
window rather than a 400-year window. For the current data, this
affects only the Asia/Tehran file. It does not affect any of the
time stamps that this file represents, so zdump outputs the same
information as before. (Thanks to Andrew Main (Zefram).)

The 'date' command has a new '-r' option, which lets you specify
the integer time to display, a la FreeBSD.

The 'tzselect' command has two new options '-c' and '-n', which lets you
select a zone based on latitude and longitude.

The 'zic' command's '-v' option now warns about constructs that
require the new version-3 binary file format. (Thanks to Arthur
David Olson for the suggestion.)

Support for floating-point time_t has been removed.
It was always dicey, and POSIX no longer requires it.
(Thanks to Eric Blake for suggesting to the POSIX committee to
remove it, and thanks to Alan Barrett, Clive D.W. Feather, Andy
Heninger, Arthur David Olson, and Alois Treindl, for reporting
bugs and elucidating some of the corners of the old floating-point
implementation.)

The signatures of 'offtime', 'timeoff', and 'gtime' have been
changed back to the old practice of using 'long' to represent UT
offsets. This had been inadvertently and mistakenly changed to
'int_fast32_t'. (Thanks to Christos Zoulos.)

The code avoids undefined behavior on integer overflow in some
more places, including gmtime, localtime, mktime and zdump.

Changes affecting the zdump utility

zdump now outputs "UT" when referring to Universal Time, not "UTC".
"UTC" does not make sense for time stamps that predate the introduction
of UTC, whereas "UT", a more-generic term, does. (Thanks to Steve Allen
for clarifying UT vs UTC.)

Data changes affecting behavior of tzselect and similar programs

Country code BQ is now called the more-common name "Caribbean Netherlands"
rather than the more-official "Bonaire, St Eustatius & Saba".

Remove from zone.tab the names America/Montreal, America/Shiprock,
and Antarctica/South_Pole, as they are equivalent to existing
same-country-code zones for post-1970 time stamps. The data for
these names are unchanged, so the names continue to work as before.

Changes affecting code internals

zic -c now runs way faster on 64-bit hosts when given large numbers.

zic now uses vfprintf to avoid allocating and freeing some memory.

tzselect now computes the list of continents from the data,
rather than have it hard-coded.

Minor changes pacify GCC 4.7.3 and GCC 4.8.1.

Changes affecting the build procedure

The 'leapseconds' file is now generated automatically from a
new file 'leap-seconds.list', which is a copy of
<ftp://time.nist.gov/pub/leap-seconds.list>.
A new source file 'leapseconds.awk' implements this.
The goal is simplification of the future maintenance of 'leapseconds'.

When building the 'posix' or 'right' subdirectories, if the
subdirectory would be a copy of the default subdirectory, it is
now made a symbolic link if that is supported. This saves about
2 MB of file system space.

The links America/Shiprock and Antarctica/South_Pole have been
moved to the 'backward' file. This affects only nondefault builds
that omit 'backward'.

Changes affecting documentation and commentary

Changes to the 'tzfile' man page

It now mentions that the binary file format may be extended in
future versions by appending data.

It now refers to the 'zdump' and 'zic' man pages.

Changes to the 'zic' man page

It lists conditions that elicit a warning with '-v'.

It says that the behavior is unspecified when duplicate names
are given, or if the source of one link is the target of another.

Its examples are updated to match the latest data.

The definition of white space has been clarified slightly.
(Thanks to Michael Deckers.)

Changes to the 'Theory' file

There is a new section about the accuracy of the tz database,
describing the many ways that errors can creep in, and
explaining why so many of the pre-1970 time stamps are wrong or
misleading (thanks to Steve Allen, Lester Caine, and Garrett
Wollman for discussions that contributed to this).

The 'Theory' file describes LMT better (this follows a
suggestion by Guy Harris).

It refers to the 2013 edition of POSIX rather than the 2004 edition.

It's mentioned that excluding 'backward' should not affect the
other data, and it suggests at least one zone.tab name per
inhabited country (thanks to Stephen Colebourne).

Some longstanding restrictions on names are documented, e.g.,
'America/New_York' precludes 'America/New_York/Bronx'.

It gives more reasons for the 1970 cutoff.

It now mentions which time_t variants are supported, such as
signed integer time_t. (Thanks to Paul Goyette for reporting
typos in an experimental version of this change.)

(Thanks to Philip Newton for correcting typos in these changes.)

Documentation and commentary is more careful to distinguish UT in
general from UTC in particular. (Thanks to Steve Allen.)

Add a better source for the Zurich 1894 transition.
(Thanks to Pierre-Yves Berger.)

Update shapefile citations in tz-link.htm. (Thanks to Guy Harris.)

branches: 1.20.2;
merge 2012e

branches: 1.19.2;
bring in the 2011i changes.

New sentence, new line.

Fix up mix of man(7)/mdoc(7).

Import tzcode2009k.
- now understands 64bit time_t and 64bit data in timezone files.
- localtime(), gmtime(), asctime() and ctime() may now fail with
a NULL result if time_t cannot be represented by struct tm.

Fix preamble to match order set out by mdoc(7). Discussed with wiz.

branches: 1.14.42;
Merge tzcode2003e.

Merge tzcode2003d.

Use a better width argument.

Generate <>& symbolically. I'm avoiding .../dist/... directories for now.

mdoc'ify

branches: 1.9.6;
Merge tzcode1999i.

branches: 1.8.6;
Merge tzcode1998h.

sync with tzcode1998a

Sync with tzcode1997e

alternate -> alternative, per PR 2643

sync with tzcode96a

/usr/local/etc/zoneinfo -> /usr/share/zoneinfo; PR #1398

branches: 1.2.2;
Added NetBSD Id.
Removed "new" from newctime(3) references.

branches: 1.1.1;
Initial revision

Fix formatting corruption for manpages from tzcode.

Comment out .TH macros, that cause mandoc(1) to run into man(7) mode.

Merge in 2022g:

Although tzcode still works with C89, bugs found in recent routine
maintenance indicate that bitrot has set in and that in practice
C89 is no longer used to build tzcode. As it is a maintenance
burden, support for C89 is planned to be removed soon. Instead,
please use compilers compatible with C99, C11, C17, or C23.

timegm, which tzcode implemented in 1989, will finally be
standardized 34 years later as part of C23, so timegm is now
supported even if STD_INSPIRED is not defined.

Fix bug in zdump's tzalloc emulation on hosts that lack tm_zone.
(Problem reported by ��o��n Tr���n C��ng Danh.)

Fix bug in zic on hosts where malloc(0) yields NULL on success.
(Problem reported by Tim McBrayer for AIX 6.1.)

Fix zic configuration to avoid linkage failures on some platforms.
(Problems reported by Gilmore Davidson and Igor Ivanov.)

Work around MS-Windows nmake incompatibility with POSIX.
(Problem reported by Manuela Friedrich.)

Port mktime and strftime to debugging platforms where accessing
uninitialized data has undefined behavior (strftime problem
reported by Robert Elz).

Check more carefully for unlikely integer overflows, preferring
C23 <stdckdint.h> to overflow checking by hand, as the latter has
had obscure bugs.

Update to tzcode2022f

Changes to code

zic now supports links to links regardless of input line order.
For example, if Australia/Sydney is a Zone, the lines
Link Australia/Canberra Australia/ACT
Link Australia/Sydney Australia/Canberra
now work correctly, even though the shell commands
ln Australia/Canberra Australia/ACT
ln Australia/Sydney Australia/Canberra
would fail because the first command attempts to use a link
Australia/Canberra that does not exist until after the second
command is executed. Previously, zic had unspecified behavior if
a Link line's target was another link, and zic often misbehaved if
a Link line's target was a later Link line.

Fix line number in zic's diagnostic for a link to a link.

Fix a bug that caused localtime to mishandle timestamps starting
in the year 2438 when reading data generated by 'zic -b fat' when
distant-future DST transitions occur at times given in standard
time or in UT, not the usual case of local time. This occurs when
the corresponding .zi Rule lines specify DST transitions with TO
columns of 'max' and AT columns that end in 's' or 'u'. The
number 2438 comes from the 32-bit limit in the year 2038, plus the
400-year Gregorian cycle. (Problem reported by Bradley White.)

On glibc 2.34 and later, which optionally supports 64-bit time_t
on platforms like x86 where time_t was traditionally 32 bits,
default time_t to 64 instead of 32 bits. This lets functions like
localtime support timestamps after the year 2038, and fixes
year-2038 problems in zic when accessing files dated after 2038.
To continue to limit time_t to 32 bits on these platforms, use
"make CFLAGS='-D_TIME_BITS=32'".

In C code, do not enable large-file support on platforms like AIX
and macOS that no longer need it now that tzcode does not use
off_t or related functions like 'stat'. Large-file support is
still enabled by default on GNU/Linux, as it is needed for 64-bit
time_t support.

In C code, prefer C23 keywords to pre-C23 macros for alignof,
bool, false, and true. Also, use the following C23 features if
available: __has_include, unreachable.

zic no longer works around Qt bug 53071, as the relevant Qt
releases have been out of support since 2019. This change affects
only fat TZif files, as thin files never had the workaround.

zdump no longer modifies the environ vector when compiled on
platforms lacking tm_zone or when compiled with -DUSE_LTZ=0.
This avoid undefined behavior on POSIX platforms.

add missing text.

Welcome to 2022b:

zic has a new option '-R @N' to output explicit transitions < N.
(Need suggested by Almaz Mingaleev.)

'zic -r @N' no longer outputs bad data when N < first transition.
(Problem introduced in 2021d and reported by Peter Krefting.)

zic now checks its input for NUL bytes and unterminated lines, and
now supports input line lengths up to 2048 (not 512) bytes.

gmtime and related code now use the abbreviation "UTC" not "GMT".
POSIX is being revised to require this.

When tzset and related functions set vestigial static variables
like tzname, they now prefer specified timestamps to unspecified ones.
(Problem reported by Almaz Mingaleev.)

zic no longer complains "can't determine time zone abbreviation to
use just after until time" when a transition to a new standard
time occurs simultanously with the first DST fallback transition.

Change to code and documentation from 2021a -> 2021e

Release 2021e - 2021-10-21 18:41:00 -0700

Changes to code

none


Release 2021d - 2021-10-15 13:48:18 -0700

Changes to code

'zic -r' now uses "-00" time zone abbreviations for intervals
with UT offsets that are unspecified due to -r truncation.
This implements a change in draft Internet RFC 8536bis.


Release 2021c - 2021-10-01 14:21:49 -0700

Changes to code

Fix a bug in 'zic -b fat' that caused old timestamps to be
mishandled in 32-bit-only readers (problem reported by Daniel
Fischer).

Changes to documentation

Distribute the SECURITY file (problem reported by Andreas Radke).


Release 2021b - 2021-09-24 16:23:00 -0700

Changes to maintenance procedure

The new file SECURITY covers how to report security-related bugs.

Several backward-compatibility links have been moved to the
'backward' file. These links, which range from Africa/Addis_Ababa
to Pacific/Saipan, are only for compatibility with now-obsolete
guidelines suggesting an entry for every ISO 3166 code.
The intercontinental convenience links Asia/Istanbul and
Europe/Nicosia have also been moved to 'backward'.

Changes to code

zic now creates each output file or link atomically,
possibly by creating a temporary file and then renaming it.
This avoids races where a TZ setting would temporarily stop
working while zic was installing a replacement file or link.

zic -L no longer omits the POSIX TZ string in its output.
Starting with 2020a, zic -L truncated its output according to the
"Expires" directive or "#expires" comment in the leapseconds file.
The resulting TZif files omitted daylight saving transitions after
the leap second table expired, which led to far less-accurate
predictions of times after the expiry. Although future timestamps
cannot be converted accurately in the presence of leap seconds, it
is more accurate to convert near-future timestamps with a few
seconds error than with an hour error, so zic -L no longer
truncates output in this way.

Instead, when zic -L is given the "Expires" directive, it now
outputs the expiration by appending a no-change entry to the leap
second table. Although this should work well with most TZif
readers, it does not conform to Internet RFC 8536 and some pickier
clients (including tzdb 2017c through 2021a) reject it, so
"Expires" directives are currently disabled by default. To enable
them, set the EXPIRES_LINE Makefile variable. If a TZif file uses
this new feature it is marked with a new TZif version number 4,
a format intended to be documented in a successor to RFC 8536.

zic -L LEAPFILE -r @LO no longer generates an invalid TZif file
that omits leap second information for the range LO..B when LO
falls between two leap seconds A and B. Instead, it generates a
TZif version 4 file that represents the previously-missing
information.

The TZif reader now allows the leap second table to begin with a
correction other than -1 or +1, and to contain adjacent
transitions with equal corrections. This supports TZif version 4.

The TZif reader now lets leap seconds occur less than 28 days
apart. This supports possible future TZif extensions.

Fix bug that caused 'localtime' etc. to crash when TZ was
set to a all-year DST string like "EST5EDT4,0/0,J365/25" that does
not conform to POSIX but does conform to Internet RFC 8536.

Fix another bug that caused 'localtime' etc. to crash when TZ was
set to a POSIX-conforming but unusual TZ string like
"EST5EDT4,0/0,J365/0", where almost all the year is DST.

Fix yet another bug that caused 'localtime' etc. to mishandle slim
TZif files containing leap seconds after the last explicit
transition in the table, or when handling far-future timestamps
in slim TZif files lacking leap seconds.

Fix localtime misbehavior involving positive leap seconds.
This change affects only behavior for "right" system time,
which contains leap seconds, and only if the UT offset is
not a multiple of 60 seconds when a positive leap second occurs.
(No such timezone exists in tzdb, luckily.) Without the fix,
the timestamp was ambiguous during a positive leap second.
With the fix, any seconds occurring after a positive leap second
and within the same localtime minute are counted through 60, not
through 59; their UT offset (tm_gmtoff) is the same as before.
Here is how the fix affects timestamps in a timezone with UT
offset +01:23:45 (5025 seconds) and with a positive leap second at
1972-06-30 23:59:60 UTC (78796800):

time_t without the fix with the fix
78796800 1972-07-01 01:23:45 1972-07-01 01:23:45 (leap second)
78796801 1972-07-01 01:23:45 1972-07-01 01:23:46
...
78796815 1972-07-01 01:23:59 1972-07-01 01:23:60
78796816 1972-07-01 01:24:00 1972-07-01 01:24:00

Fix an unlikely bug that caused 'localtime' etc. to misbehave if
civil time changes a few seconds before time_t wraps around, when
leap seconds are enabled.

Fix bug in zic -r; in some cases, the dummy time type after the
last time transition disagreed with the TZ string, contrary to
Internet RFC 8563 section 3.3.

Fix a bug with 'zic -r @X' when X is a negative leap second that
has a nonnegative correction. Without the fix, the output file
was truncated so that X appeared to be a positive leap second.
Fix a similar, even-less-likely bug when truncating at a positive
leap second that has a nonpositive correction.

zic -r now reports an error if given rolling leap seconds, as this
usage has never generally worked and is evidently unused.

zic now generates a POSIX-conforming TZ string for TZif files
where all-year DST is predicted for the indefinite future.
For example, for all-year Eastern Daylight Time, zic now generates
"XXX3EDT4,0/0,J365/23" where it previously generated
"EST5EDT,0/0,J365/25" or "". (Thanks to Michael Deckers for
noting the possibility of POSIX conformance.)

zic.c no longer requires sys/wait.h (thanks to spazmodius for
noting it wasn't needed).

When reading slim TZif files, zdump no longer mishandles leap
seconds on the rare platforms where time_t counts leap seconds,
fixing a bug introduced in 2014g.

zdump -v now outputs timestamps at boundaries of what localtime
and gmtime can represent, instead of the less-useful timestamps
one day after the minimum and one day before the maximum.
(Thanks to Arthur David Olson for prototype code, and to Manuela
Friedrich for debugging help.)

zdump's -c and -t options are now consistently inclusive for the
lower time bound and exclusive for the upper. Formerly they were
inconsistent. (Confusion noted by Martin Burnicki.)

Changes to build procedure

You can now compile with -DHAVE_MALLOC_ERRNO=0 to port to
non-POSIX hosts where malloc doesn't set errno.
(Problem reported by Jan Engelhardt.)

Changes to documentation

tzfile.5 better matches a draft successor to RFC 8536
<https://datatracker.ietf.org/doc/draft-murchison-rfc8536bis/01/>.

Merge tzcode-2021a
- No comments in the changelog about the code changes.

Merge tzcode2020b (except we keep tzsetwall(3) for now for compatibility,
and we were "slim" already)

Support for zic's long-obsolete '-y YEARISTYPE' option has been
removed and, with it, so has support for the TYPE field in Rule
lines, which is now reserved for compatibility with earlier zic.
These features were previously deprecated in release 2015f.
(Thanks to Tim Parenti.)

zic now defaults to '-b slim' instead of to '-b fat'.

zic's new '-l -' and '-p -' options uninstall any existing
localtime and posixrules files, respectively.

The undocumented and ineffective tzsetwall function has been
removed.

Bring in 2020a

Sync with 2019b:

zic's new -b option supports a way to control data bloat and to
test for year-2038 bugs in software that reads TZif files.
'zic -b fat' and 'zic -b slim' generate larger and smaller output;
for example, changing from fat to slim shrinks the Europe/London
file from 3648 to 1599 bytes, saving about 56%. Fat and slim
files represent the same set of timestamps and use the same TZif
format as documented in tzfile(5) and in Internet RFC 8536.
Fat format attempts to work around bugs or incompatibilities in
older software, notably software that mishandles 64-bit TZif data
or uses obsolete TZ strings like "EET-2EEST" that lack DST rules.
Slim format is more efficient and does not work around 64-bit bugs
or obsolete TZ strings. Currently zic defaults to fat format
unless you compile with -DZIC_BLOAT_DEFAULT=\"slim\"; this
out-of-the-box default is intended to change in future releases
as the buggy software often mishandles timestamps anyway.

zic no longer treats a set of rules ending in 2037 specially.
Previously, zic assumed that such a ruleset meant that future
timestamps could not be predicted, and therefore omitted a
POSIX-like TZ string in the TZif output. The old behavior is no
longer needed for current tzdata, and caused problems with newlib
when used with older tzdata (reported by David Gauchard).

zic no longer generates some artifact transitions. For example,
Europe/London no longer has a no-op transition in January 1996.

merge 2019a

Changes to code

zic now has an -r option to limit the time range of output data.
For example, 'zic -r @1000000000' limits the output data to
timestamps starting 1000000000 seconds after the Epoch.
This helps shrink output size and can be useful for applications
not needing the full timestamp history, such as TZDIST truncation;
see Internet RFC 8536 section 5.1. (Inspired by a feature request
from Christopher Wong, helped along by bug reports from Wong and
from Tim Parenti.)

Changes to documentation

Mention Internet RFC 8536 (February 2019), which documents TZif.

tz-link.html now cites tzdata-meta
<https://tzdata-meta.timtimeonline.com/>.

Welcome tzcode-2018g

Changes to code

When generating TZif files with leap seconds, zic no longer uses a
format that trips up older 32-bit clients, fixing a bug introduced
in 2018f. (Reported by Daniel Fischer.) Also, the zic workaround
for QTBUG-53071 now also works for TZif files with leap seconds.

The translator to rearguard format now rewrites the line
"Rule Japan 1948 1951 - Sep Sat>=8 25:00 0 S" to
"Rule Japan 1948 1951 - Sep Sun>=9 1:00 0 S".
This caters to zic before 2007 and to Oracle TZUpdater 2.2.0
and earlier. (Reported by Christos Zoulas.)

Changes to documentation

tzfile.5 has new sections on interoperability issues.

Update to 2018f:

Changes to code

zic now always generates TZif files where time type 0 is used for
timestamps before the first transition. This simplifies the
reading of TZif files and should not affect behavior of existing
TZif readers because the same set of time types is used; only
their internal indexes may have changed. This affects only the
legacy zones EST5EDT, CST6CDT, MST7MDT, PST8PDT, CET, MET, and
EET, which previously used nonzero types for these timestamps.

Because of the type 0 change, zic no longer outputs a dummy
transition at time -2**59 (before the Big Bang), as clients should
no longer need this to handle historical timestamps correctly.
This reverts a change introduced in 2013d and shrinks most TZif
files by a few bytes.

zic now supports negative time-of-day in Rule and Leap lines, e.g.,
"Rule X min max - Apr lastSun -6:00 1:00 -" means the transition
occurs at 18:00 on the Saturday before the last Sunday in April.
This behavior was documented in 2018a but the code did not
entirely match the documentation.

localtime.c no longer requires at least one time type in TZif
files that lack transitions or have a POSIX-style TZ string. This
future-proofs the code against possible future extensions to the
format that would allow TZif files with POSIX-style TZ strings and
without transitions or time types.

A read-access subscript error in localtime.c has been fixed.
It could occur only in TZif files with timecnt == 0, something that
does not happen in practice now but could happen in future versions.

localtime.c no longer ignores TZif POSIX-style TZ strings that
specify only standard time. Instead, these TZ strings now
override the default time type for timestamps after the last
transition (or for all time stamps if there are no transitions),
just as DST strings specifying DST have always done.

leapseconds.awk now outputs "#updated" and "#expires" comments,
and supports leap seconds at the ends of months other than June
and December. (Inspired by suggestions from Chris Woodbury.)

Changes to documentation

New restrictions: A Rule name must start with a character that
is neither an ASCII digit nor "-" nor "+", and an unquoted name
should not use characters in the set "!$%&'()*,/:;<=>?@[\]^`{|}~".
The latter restriction makes room for future extensions (a
possibility noted by Tom Lane).

tzfile.5 now documents what time types apply before the first and
after the last transition, if any.

Documentation now uses the spelling "timezone" for a TZ setting
that determines timestamp history, and "time zone" for a
geographic region currently sharing the same standard time.

The name "TZif" is now used for the tz binary data format.

tz-link.htm now mentions the A0 TimeZone Migration utilities.
(Thanks to Aldrin Martoq for the link.)

branches: 1.29.2;
Merge 2018e

Changes to code

zic now accepts subsecond precision in expressions like
00:19:32.13, which is approximately the legal time of the
Netherlands from 1835 to 1937. However, because it is
questionable whether the few recorded uses of non-integer offsets
had subsecond precision in practice, there are no plans for tzdata
to use this feature. (Thanks to Steve Allen for pointing out
the limitations of historical data in this area.)

The code is a bit more portable to MS-Windows. Installers can
compile with -DRESERVE_STD_EXT_IDS on MS-Windows platforms that
reserve identifiers like 'localtime'. (Thanks to Manuela
Friedrich).

Changes to documentation and commentary

theory.html now outlines tzdb's extensions to POSIX's model for
civil time, and has a section "POSIX features no longer needed"
that lists POSIX API components that are now vestigial.
(From suggestions by Steve Summit.) It also better distinguishes
time zones from tz regions. (From a suggestion by Guy Harris.)

Commentary is now more consistent about using the phrase "daylight
saving time", to match the C name tm_isdst. Daylight saving time
need not occur in summer, and need not have a positive offset from
standard time.

Commentary about historical transitions in Uruguay has been expanded
with links to many relevant legal documents.
(Thanks to Tim Parenti.)

Commentary now uses some non-ASCII characters with Unicode value
less than U+0100, as they can be useful and should work even with
older editors such as XEmacs.

branches: 1.28.2;
Merge tzcode2018c [ changelog with changes to tzdata sections removed ]

Release 2018c - 2018-01-22 23:00:44 -0800

Changes to build procedure

The build procedure now works around mawk 1.3.3's lack of support
for character class expressions. (Problem reported by Ohyama.)


Release 2018b - 2018-01-17 23:24:48 -0800

Changes to build procedure

The distribution now contains the file 'pacificnew' again.
This file was inadvertantly omitted in the 2018a distribution.
(Problem reported by Matias Fonzo.)


Release 2018a - 2018-01-12 22:29:21 -0800

Changes to build procedure

The default installation locations have been changed to mostly
match Debian circa 2017, instead of being designed as an add-on to
4.3BSD circa 1986. This affects the Makefile macros TOPDIR,
TZDIR, MANDIR, and LIBDIR. New Makefile macros TZDEFAULT, USRDIR,
USRSHAREDIR, BINDIR, ZDUMPDIR, and ZICDIR let installers tailor
locations more precisely. (This responds to suggestions from
Brian Inglis and from Steve Summit.)

The default installation procedure no longer creates the
backward-compatibility link US/Pacific-New, which causes
confusion during user setup (e.g., see Debian bug 815200).
Use 'make BACKWARD="backward pacificnew"' to create the link
anyway, for now. Eventually we plan to remove the link entirely.

tzdata.zi now contains a version-number comment.
(Suggested by Tom Lane.)

The Makefile now quotes values like BACKWARD more carefully when
passing them to the shell. (Problem reported by Zefram.)

Builders no longer need to specify -DHAVE_SNPRINTF on platforms
that have snprintf and use pre-C99 compilers. (Problem reported
by Jon Skeet.)

Changes to code

zic has a new option -t FILE that specifies the location of the
file that determines local time when TZ is unset. The default for
this location can be configured via the new TZDEFAULT makefile
macro, which defaults to /etc/localtime.

Diagnostics and commentary now distinguish UT from UTC more
carefully; see theory.html for more information about UT vs UTC.

zic has been ported to GCC 8's -Wstringop-truncation option.
(Problem reported by Martin Sebor.)

Changes to documentation and commentary

The zic man page now documents the longstanding behavior that
times and years can be out of the usual range, with negative times
counting backwards from midnight and with year 0 preceding year 1.
(Problem reported by Michael Deckers.)

The theory.html file now mentions the POSIX limit of six chars
per abbreviation, and lists alphabetic abbreviations used.

The files tz-art.htm and tz-link.htm have been renamed to
tz-art.html and tz-link.html, respectively, for consistency with
other file names and to simplify web server configuration.

Welcome to 2017c:

zic and the reference runtime now reject multiple leap seconds
within 28 days of each other, or leap seconds before the Epoch.
As a result, support for double leap seconds, which was
obsolescent and undocumented, has been removed. Double leap
seconds were an error in the C89 standard; they have never existed
in civil timekeeping. (Thanks to Robert Elz and Bradley White for
noticing glitches in the code that uncovered this problem.)

zic now warns about use of the obsolescent and undocumented -y
option, and about use of the obsolescent TYPE field of Rule lines.

zic now allows unambiguous abbreviations like "Sa" and "Su" for
weekdays; formerly it rejected them due to a bug. Conversely, zic
no longer considers non-prefixes to be abbreviations; for example,
it no longer accepts "lF" as an abbreviation for "lastFriday".
Also, zic warns about the undocumented usage with a "last-"
prefix, e.g., "last-Fri".

Similarly, zic now accepts the unambiguous abbreviation "L" for
"Link" in ordinary context and for "Leap" in leap-second context.
Conversely, zic no longer accepts non-prefixes such as "La" as
abbreviations for words like "Leap".

zic no longer accepts leap second lines in ordinary input, or
ordinary lines in leap second input. Formerly, zic sometimes
warned about this undocumented usage and handled it incorrectly.

The new macro HAVE_TZNAME governs whether the tzname external
variable is exported, instead of USG_COMPAT. USG_COMPAT now
governs only the external variables "timezone" and "daylight".
This change is needed because the three variables are not in the
same category: although POSIX requires tzname, it specifies the
other two variables as optional. Also, USG_COMPAT is now 1 or 0:
if not defined, the code attempts to guess it from other macros.

localtime.c and difftime.c no longer require stdio.h, and .c files
other than zic.c no longer require sys/wait.h.

zdump.c no longer assumes snprintf. (Reported by Jonathan Leffler.)

Calculation of time_t extrema works around a bug in GCC 4.8.4
(Reported by Stan Shebs and Joseph Myers.)

zic.c no longer mistranslates formats of line numbers in non-English
locales. (Problem reported by Benno Schulenberg.)

Several minor changes have been made to the code to make it a
bit easier to port to MS-Windows and Solaris. (Thanks to Kees
Dekker for reporting the problems.)

Changes to documentation and commentary

The two new files 'theory.html' and 'calendars' contain the
contents of the removed file 'Theory'. The goal is to document
tzdb theory more accessibly.

The zic man page now documents abbreviation rules.

tz-link.htm now covers how to apply tzdata changes to clients.
(Thanks to Jorge F��bregas for the AIX link.) It also mentions MySQL.

The leap-seconds.list URL has been updated to something that is
more reliable for tzdb. (Thanks to Tim Parenti and Brian Inglis.)

merge 2015f

merge tzcode2015e:

Changes affecting code

When displaying data, tzselect converts it to the current locale's
encoding if the iconv command works. (Problem reported by random832.)

tzselect no longer mishandles Dominica, fixing a bug introduced
in Release 2014f. (Problem reported by Owen Leibman.)

zic -l no longer fails when compiled with -DTZDEFAULT=\"/etc/localtime\".
This fixes a bug introduced in Release 2014f.
(Problem reported by Leonardo Chiquitto.)

Sync with tzcode2014h

merge tzcode2014f via patch

branches: 1.22.2;
welcome to 2014d; zic big bang fixes:
some programs did not handle large negative time_t values well (gnome)

branches: 1.21.2;
Welcome to tzcode 2013e:

Changes affecting API

The 'zic' command now outputs a dummy transition when far-future
data can't be summarized using a TZ string, and uses a 402-year
window rather than a 400-year window. For the current data, this
affects only the Asia/Tehran file. It does not affect any of the
time stamps that this file represents, so zdump outputs the same
information as before. (Thanks to Andrew Main (Zefram).)

The 'date' command has a new '-r' option, which lets you specify
the integer time to display, a la FreeBSD.

The 'tzselect' command has two new options '-c' and '-n', which lets you
select a zone based on latitude and longitude.

The 'zic' command's '-v' option now warns about constructs that
require the new version-3 binary file format. (Thanks to Arthur
David Olson for the suggestion.)

Support for floating-point time_t has been removed.
It was always dicey, and POSIX no longer requires it.
(Thanks to Eric Blake for suggesting to the POSIX committee to
remove it, and thanks to Alan Barrett, Clive D.W. Feather, Andy
Heninger, Arthur David Olson, and Alois Treindl, for reporting
bugs and elucidating some of the corners of the old floating-point
implementation.)

The signatures of 'offtime', 'timeoff', and 'gtime' have been
changed back to the old practice of using 'long' to represent UT
offsets. This had been inadvertently and mistakenly changed to
'int_fast32_t'. (Thanks to Christos Zoulos.)

The code avoids undefined behavior on integer overflow in some
more places, including gmtime, localtime, mktime and zdump.

Changes affecting the zdump utility

zdump now outputs "UT" when referring to Universal Time, not "UTC".
"UTC" does not make sense for time stamps that predate the introduction
of UTC, whereas "UT", a more-generic term, does. (Thanks to Steve Allen
for clarifying UT vs UTC.)

Data changes affecting behavior of tzselect and similar programs

Country code BQ is now called the more-common name "Caribbean Netherlands"
rather than the more-official "Bonaire, St Eustatius & Saba".

Remove from zone.tab the names America/Montreal, America/Shiprock,
and Antarctica/South_Pole, as they are equivalent to existing
same-country-code zones for post-1970 time stamps. The data for
these names are unchanged, so the names continue to work as before.

Changes affecting code internals

zic -c now runs way faster on 64-bit hosts when given large numbers.

zic now uses vfprintf to avoid allocating and freeing some memory.

tzselect now computes the list of continents from the data,
rather than have it hard-coded.

Minor changes pacify GCC 4.7.3 and GCC 4.8.1.

Changes affecting the build procedure

The 'leapseconds' file is now generated automatically from a
new file 'leap-seconds.list', which is a copy of
<ftp://time.nist.gov/pub/leap-seconds.list>.
A new source file 'leapseconds.awk' implements this.
The goal is simplification of the future maintenance of 'leapseconds'.

When building the 'posix' or 'right' subdirectories, if the
subdirectory would be a copy of the default subdirectory, it is
now made a symbolic link if that is supported. This saves about
2 MB of file system space.

The links America/Shiprock and Antarctica/South_Pole have been
moved to the 'backward' file. This affects only nondefault builds
that omit 'backward'.

Changes affecting documentation and commentary

Changes to the 'tzfile' man page

It now mentions that the binary file format may be extended in
future versions by appending data.

It now refers to the 'zdump' and 'zic' man pages.

Changes to the 'zic' man page

It lists conditions that elicit a warning with '-v'.

It says that the behavior is unspecified when duplicate names
are given, or if the source of one link is the target of another.

Its examples are updated to match the latest data.

The definition of white space has been clarified slightly.
(Thanks to Michael Deckers.)

Changes to the 'Theory' file

There is a new section about the accuracy of the tz database,
describing the many ways that errors can creep in, and
explaining why so many of the pre-1970 time stamps are wrong or
misleading (thanks to Steve Allen, Lester Caine, and Garrett
Wollman for discussions that contributed to this).

The 'Theory' file describes LMT better (this follows a
suggestion by Guy Harris).

It refers to the 2013 edition of POSIX rather than the 2004 edition.

It's mentioned that excluding 'backward' should not affect the
other data, and it suggests at least one zone.tab name per
inhabited country (thanks to Stephen Colebourne).

Some longstanding restrictions on names are documented, e.g.,
'America/New_York' precludes 'America/New_York/Bronx'.

It gives more reasons for the 1970 cutoff.

It now mentions which time_t variants are supported, such as
signed integer time_t. (Thanks to Paul Goyette for reporting
typos in an experimental version of this change.)

(Thanks to Philip Newton for correcting typos in these changes.)

Documentation and commentary is more careful to distinguish UT in
general from UTC in particular. (Thanks to Steve Allen.)

Add a better source for the Zurich 1894 transition.
(Thanks to Pierre-Yves Berger.)

Update shapefile citations in tz-link.htm. (Thanks to Guy Harris.)

branches: 1.20.2;
merge 2012e

branches: 1.19.2;
bring in the 2011i changes.

New sentence, new line.

Fix up mix of man(7)/mdoc(7).

Import tzcode2009k.
- now understands 64bit time_t and 64bit data in timezone files.
- localtime(), gmtime(), asctime() and ctime() may now fail with
a NULL result if time_t cannot be represented by struct tm.

Fix preamble to match order set out by mdoc(7). Discussed with wiz.

branches: 1.14.42;
Merge tzcode2003e.

Merge tzcode2003d.

Use a better width argument.

Generate <>& symbolically. I'm avoiding .../dist/... directories for now.

mdoc'ify

branches: 1.9.6;
Merge tzcode1999i.

branches: 1.8.6;
Merge tzcode1998h.

sync with tzcode1998a

Sync with tzcode1997e

alternate -> alternative, per PR 2643

sync with tzcode96a

/usr/local/etc/zoneinfo -> /usr/share/zoneinfo; PR #1398

branches: 1.2.2;
Added NetBSD Id.
Removed "new" from newctime(3) references.

branches: 1.1.1;
Initial revision