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.

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.

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.

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.

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: 1.4.2; 1.4.4;
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.)

branches: 1.2.2;
merge tzcode2016g

welcome to tzcond-2016f

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.

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.

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.

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: 1.4.2; 1.4.4;
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.)

branches: 1.2.2;
merge tzcode2016g

welcome to tzcond-2016f

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.

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.

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: 1.4.2; 1.4.4;
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.)

branches: 1.2.2;
merge tzcode2016g

welcome to tzcond-2016f

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.

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: 1.4.2; 1.4.4;
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.)

branches: 1.2.2;
merge tzcode2016g

welcome to tzcond-2016f

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: 1.4.2;
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.)

branches: 1.2.2;
merge tzcode2016g

welcome to tzcond-2016f

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.)

branches: 1.2.2;
merge tzcode2016g

welcome to tzcond-2016f

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.)

branches: 1.2.2;
merge tzcode2016g

welcome to tzcond-2016f

branches: 1.2.2;
merge tzcode2016g

welcome to tzcond-2016f