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.

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.

Welcome to tzcode-2022c

Work around a bug in onetrueawk that broke commands like
'make traditional_tarballs' on FreeBSD, macOS, etc.
(Problem reported by Deborah Goldsmith.)

Add code to tzselect that uses experimental structured comments in
zone1970.tab to clarify whether Zones like Africa/Abidjan and
Europe/Istanbul cross continent or ocean boundaries.
(Inspired by a problem reported by Peter Krefting.)

Fix bug with 'zic -d /a/b/c' when /a is unwritable but the
directory /a/b already exists.

Remove zoneinfo2tdf.pl, as it was unused and triggered false
malware alarms on some email servers.

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.

welcome to tzcode-2022a

Changes to code

Fix bug when mktime gets confused by truncated TZif files with
unspecified local time. (Problem reported by Almaz Mingaleev.)

Fix bug when 32-bit time_t code reads malformed 64-bit TZif data.
(Problem reported by Christos Zoulas.)

When reading a version 2 or later TZif file, the TZif reader now
validates the version 1 header and data block only enough to skip
over them, as recommended by RFC 8536 section 4. Also, the TZif
reader no longer mistakenly attempts to parse a version 1 TZIf
file header as a TZ string.

zdump -v now outputs "(localtime failed)" and "(gmtime failed)"
when local time and UT cannot be determined for a timestamp.

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.

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: 1.7.2; 1.7.4;
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.

merge tzcode2014f via patch

branches: 1.5.4;
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: 1.4.6; 1.4.12;
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.

Merge tzcode1999h.

branches: 1.2.6;
RCS Id Police.

branches: 1.1.1;
Initial revision

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.

Welcome to tzcode-2022c

Work around a bug in onetrueawk that broke commands like
'make traditional_tarballs' on FreeBSD, macOS, etc.
(Problem reported by Deborah Goldsmith.)

Add code to tzselect that uses experimental structured comments in
zone1970.tab to clarify whether Zones like Africa/Abidjan and
Europe/Istanbul cross continent or ocean boundaries.
(Inspired by a problem reported by Peter Krefting.)

Fix bug with 'zic -d /a/b/c' when /a is unwritable but the
directory /a/b already exists.

Remove zoneinfo2tdf.pl, as it was unused and triggered false
malware alarms on some email servers.

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.

welcome to tzcode-2022a

Changes to code

Fix bug when mktime gets confused by truncated TZif files with
unspecified local time. (Problem reported by Almaz Mingaleev.)

Fix bug when 32-bit time_t code reads malformed 64-bit TZif data.
(Problem reported by Christos Zoulas.)

When reading a version 2 or later TZif file, the TZif reader now
validates the version 1 header and data block only enough to skip
over them, as recommended by RFC 8536 section 4. Also, the TZif
reader no longer mistakenly attempts to parse a version 1 TZIf
file header as a TZ string.

zdump -v now outputs "(localtime failed)" and "(gmtime failed)"
when local time and UT cannot be determined for a timestamp.

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.

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: 1.7.2; 1.7.4;
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.

merge tzcode2014f via patch

branches: 1.5.4;
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: 1.4.6; 1.4.12;
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.

Merge tzcode1999h.

branches: 1.2.6;
RCS Id Police.

branches: 1.1.1;
Initial revision

Welcome to tzcode-2022c

Work around a bug in onetrueawk that broke commands like
'make traditional_tarballs' on FreeBSD, macOS, etc.
(Problem reported by Deborah Goldsmith.)

Add code to tzselect that uses experimental structured comments in
zone1970.tab to clarify whether Zones like Africa/Abidjan and
Europe/Istanbul cross continent or ocean boundaries.
(Inspired by a problem reported by Peter Krefting.)

Fix bug with 'zic -d /a/b/c' when /a is unwritable but the
directory /a/b already exists.

Remove zoneinfo2tdf.pl, as it was unused and triggered false
malware alarms on some email servers.

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.

welcome to tzcode-2022a

Changes to code

Fix bug when mktime gets confused by truncated TZif files with
unspecified local time. (Problem reported by Almaz Mingaleev.)

Fix bug when 32-bit time_t code reads malformed 64-bit TZif data.
(Problem reported by Christos Zoulas.)

When reading a version 2 or later TZif file, the TZif reader now
validates the version 1 header and data block only enough to skip
over them, as recommended by RFC 8536 section 4. Also, the TZif
reader no longer mistakenly attempts to parse a version 1 TZIf
file header as a TZ string.

zdump -v now outputs "(localtime failed)" and "(gmtime failed)"
when local time and UT cannot be determined for a timestamp.

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.

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: 1.7.2; 1.7.4;
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.

merge tzcode2014f via patch

branches: 1.5.4;
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: 1.4.6; 1.4.12;
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.

Merge tzcode1999h.

branches: 1.2.6;
RCS Id Police.

branches: 1.1.1;
Initial revision

welcome to tzcode-2022a

Changes to code

Fix bug when mktime gets confused by truncated TZif files with
unspecified local time. (Problem reported by Almaz Mingaleev.)

Fix bug when 32-bit time_t code reads malformed 64-bit TZif data.
(Problem reported by Christos Zoulas.)

When reading a version 2 or later TZif file, the TZif reader now
validates the version 1 header and data block only enough to skip
over them, as recommended by RFC 8536 section 4. Also, the TZif
reader no longer mistakenly attempts to parse a version 1 TZIf
file header as a TZ string.

zdump -v now outputs "(localtime failed)" and "(gmtime failed)"
when local time and UT cannot be determined for a timestamp.

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.

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: 1.7.2; 1.7.4;
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.

merge tzcode2014f via patch

branches: 1.5.4;
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: 1.4.6; 1.4.12;
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.

Merge tzcode1999h.

branches: 1.2.6;
RCS Id Police.

branches: 1.1.1;
Initial revision

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.

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: 1.7.2; 1.7.4;
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.

merge tzcode2014f via patch

branches: 1.5.4;
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: 1.4.6; 1.4.12;
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.

Merge tzcode1999h.

branches: 1.2.6;
RCS Id Police.

branches: 1.1.1;
Initial revision

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: 1.7.2;
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.

merge tzcode2014f via patch

branches: 1.5.4;
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: 1.4.6; 1.4.12;
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.

Merge tzcode1999h.

branches: 1.2.6;
RCS Id Police.

branches: 1.1.1;
Initial revision

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.

merge tzcode2014f via patch

branches: 1.5.4;
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: 1.4.6; 1.4.12;
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.

Merge tzcode1999h.

branches: 1.2.6;
RCS Id Police.

branches: 1.1.1;
Initial revision