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NEWS
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News for the tz database
Unreleased, experimental changes
Briefly:
System V names are now obsolescent.
The main data form now uses %z.
The code now conforms to RFC 8536 for early timestamps.
Support POSIX.1-2024, which removes asctime_r and ctime_r.
Assume POSIX.2-1992 or later for shell scripts.
Improve historical data for Portugal and possessions.
Changes to data
Names present only for compatibility with UNIX System V
(last released in the 1990s) have been moved to 'backward'.
These names, which for post-1970 timestamps mostly just duplicate
data of geographical names, were confusing downstream uses.
Names moved to 'backward' are now links to geographical names.
This affects behavior for TZ='EET' for some pre-1981 timestamps,
for TZ='CET' for some pre-1947 timestamps, and for TZ='WET' for
some pre-1996 timestamps. Also, TZ='MET' now behaves like
TZ='CET' and so uses the abbreviation "CET" rather than "MET".
Those needing the previous TZDB behavior, which does not match any
real-world clocks, can find the old entries in 'backzone'.
(Problem reported by Justin Grant.)
The main source files' time zone abbreviations now use %z,
supported by zic since release 2015f and used in vanguard form
since release 2022b. For example, America/Sao_Paulo now contains
the zone continuation line "-3:00 Brazil %z", which is less error
prone than the old "-3:00 Brazil -03/-02". This does not change
the represented data: the generated TZif files are unchanged.
Rearguard form still avoids %z, to support obsolescent parsers.
Some transitions for Portugal and possessions have been changed.
This affects timestamps for Africa/Maputo before 1909.
Asia/Almaty has been removed from zonenow.tab as it now agrees
with Asia/Tashkent for future timestamps, due to Kazakhstan's
2024-02-29 time zone change. Similarly, America/Scoresbysund
has been removed, as it now agrees with America/Nuuk due to
its 2024-03-31 time zone change.
Changes to code
localtime.c now always uses a TZif file's time type 0 to handle
timestamps before the file's first transition. Formerly,
localtime.c sometimes inferred a different time type, in order to
handle problematic data generated by zic 2018e or earlier. As it
is now safe to assume more recent versions of zic, there is no
longer a pressing need to fail to conform RFC 8536 section 3.2,
which requires using time type 0 in this situation. This change
does not affect behavior when reading TZif files generated by zic
2018f and later.
POSIX.1-2024 removes asctime_r and ctime_r and does not let
libraries define them, so remove them except when needed to
conform to earlier POSIX. These functions are dangerous as they
can overrun user buffers. If you still need them, add
-DSUPPORT_POSIX2008 to CFLAGS.
tzselect now assumes POSIX.2-1992 or later, as practical porting
targets now all support this. Also, tzselect uses some features
from POSIX.1-2024 if available.
Changes to build procedure
'make check' no longer requires curl and Internet access.
The build procedure now assumes POSIX.2-1992 or later, to simplify
maintenance. To build on Solaris 10, the only extant system still
defaulting to pre-POSIX, prepend /usr/xpg4/bin to PATH.
Release 2024a - 2024-02-01 09:28:56 -0800
Briefly:
Kazakhstan unifies on UTC+5 beginning 2024-03-01.
Palestine springs forward a week later after Ramadan.
zic no longer pretends to support indefinite-past DST.
localtime no longer mishandles Ciudad Juárez in 2422.
Changes to future timestamps
Kazakhstan unifies on UTC+5. This affects Asia/Almaty and
Asia/Qostanay which together represent the eastern portion of the
country that will transition from UTC+6 on 2024-03-01 at 00:00 to
join the western portion. (Thanks to Zhanbolat Raimbekov.)
Palestine springs forward a week later than previously predicted
in 2024 and 2025. (Thanks to Heba Hamad.) Change spring-forward
predictions to the second Saturday after Ramadan, not the first;
this also affects other predictions starting in 2039.
Changes to past timestamps
Asia/Ho_Chi_Minh's 1955-07-01 transition occurred at 01:00
not 00:00. (Thanks to Đoàn Trần Công Danh.)
From 1947 through 1949, Toronto's transitions occurred at 02:00
not 00:00. (Thanks to Chris Walton.)
In 1911 Miquelon adopted standard time on June 15, not May 15.
Changes to code
The FROM and TO columns of Rule lines can no longer be "minimum"
or an abbreviation of "minimum", because TZif files do not support
DST rules that extend into the indefinite past - although these
rules were supported when TZif files had only 32-bit data, this
stopped working when 64-bit TZif files were introduced in 1995.
This should not be a problem for realistic data, since DST was
first used in the 20th century. As a transition aid, FROM columns
like "minimum" are now diagnosed and then treated as if they were
the year 1900; this should suffice for TZif files on old systems
with only 32-bit time_t, and it is more compatible with bugs in
2023c-and-earlier localtime.c. (Problem reported by Yoshito
Umaoka.)
localtime and related functions no longer mishandle some
timestamps that occur about 400 years after a switch to a time
zone with a DST schedule. In 2023d data this problem was visible
for some timestamps in November 2422, November 2822, etc. in
America/Ciudad_Juarez. (Problem reported by Gilmore Davidson.)
strftime %s now uses tm_gmtoff if available. (Problem and draft
patch reported by Dag-Erling Smørgrav.)
Changes to build procedure
The leap-seconds.list file is now copied from the IERS instead of
from its downstream counterpart at NIST, as the IERS version is
now in the public domain too and tends to be more up-to-date.
(Thanks to Martin Burnicki for liaisoning with the IERS.)
Changes to documentation
The strftime man page documents which struct tm members affect
which conversion specs, and that tzset is called. (Problems
reported by Robert Elz and Steve Summit.)
Release 2023d - 2023-12-21 20:02:24 -0800
Briefly:
Ittoqqortoormiit, Greenland changes time zones on 2024-03-31.
Vostok, Antarctica changed time zones on 2023-12-18.
Casey, Antarctica changed time zones five times since 2020.
Code and data fixes for Palestine timestamps starting in 2072.
A new data file zonenow.tab for timestamps starting now.
Changes to future timestamps
Ittoqqortoormiit, Greenland (America/Scoresbysund) joins most of
the rest of Greenland's timekeeping practice on 2024-03-31, by
changing its time zone from -01/+00 to -02/-01 at the same moment
as the spring-forward transition. Its clocks will therefore not
spring forward as previously scheduled. The time zone change
reverts to its common practice before 1981.
Fix predictions for DST transitions in Palestine in 2072-2075,
correcting a typo introduced in 2023a.
Changes to past and future timestamps
Vostok, Antarctica changed to +05 on 2023-12-18. It had been at
+07 (not +06) for years. (Thanks to Zakhary V. Akulov.)
Change data for Casey, Antarctica to agree with timeanddate.com,
by adding five time zone changes since 2020. Casey is now at +08
instead of +11.
Changes to past tm_isdst flags
Much of Greenland, represented by America/Nuuk, changed its
standard time from -03 to -02 on 2023-03-25, not on 2023-10-28.
This does not affect UTC offsets, only the tm_isdst flag.
(Thanks to Thomas M. Steenholdt.)
New data file
A new data file zonenow.tab helps configure applications that use
timestamps dated from now on. This simplifies configuration,
since users choose from a smaller Zone set. The file's format is
experimental and subject to change.
Changes to code
localtime.c no longer mishandles TZif files that contain a single
transition into a DST regime. Previously, it incorrectly assumed
DST was in effect before the transition too. (Thanks to Alois
Treindl for debugging help.)
localtime.c's timeoff no longer collides with OpenBSD 7.4.
The C code now uses _Generic only if __STDC_VERSION__ says the
compiler is C11 or later.
tzselect now optionally reads zonenow.tab, to simplify when
configuring only for timestamps dated from now on.
tzselect no longer creates temporary files.
tzselect no longer mishandles the following:
Spaces and most other special characters in BUGEMAIL, PACKAGE,
TZDIR, and VERSION.
TZ strings when using mawk 1.4.3, which mishandles regular
expressions of the form /X{2,}/.
ISO 6709 coordinates when using an awk that lacks the GNU
extension of newlines in -v option-arguments.
Non UTF-8 locales when using an iconv command that lacks the GNU
//TRANSLIT extension.
zic no longer mishandles data for Palestine after the year 2075.
Previously, it incorrectly omitted post-2075 transitions that are
predicted for just before and just after Ramadan. (Thanks to Ken
Murchison for debugging help.)
zic now works again on Linux 2.6.16 and 2.6.17 (2006).
(Problem reported by Rune Torgersen.)
Changes to build procedure
The Makefile is now more compatible with POSIX:
* It no longer defines AR, CC, CFLAGS, LDFLAGS, and SHELL.
* It no longer uses its own 'cc' in place of CC.
* It now uses ARFLAGS, with default specified by POSIX.
* It does not use LFLAGS incompatibly with POSIX.
* It uses the special .POSIX target.
* It quotes special characters more carefully.
* It no longer mishandles builds in an ISO 8859 locale.
Due to the CC changes, TZDIR is now #defined in a file tzdir.h
built by 'make', not in a $(CC) -D option. Also, TZDEFAULT is
now treated like TZDIR as they have similar roles.
Changes to commentary
Limitations and hazards of the optional support for obsolescent
C89 platforms are documented better, along with a tentative
schedule for removing this support.
Release 2023c - 2023-03-28 12:42:14 -0700
Changes to past and future timestamps
Model Lebanon's DST chaos by reverting data to tzdb 2023a.
(Thanks to Rany Hany for the heads-up.)
Release 2023b - 2023-03-23 19:50:38 -0700
Changes to future timestamps
This year Lebanon springs forward April 20/21 not March 25/26.
(Thanks to Saadallah Itani.) [This was reverted in 2023c.]
Release 2023a - 2023-03-22 12:39:33 -0700
Briefly:
Egypt now uses DST again, from April through October.
This year Morocco springs forward April 23, not April 30.
Palestine delays the start of DST this year.
Much of Greenland still uses DST from 2024 on.
America/Yellowknife now links to America/Edmonton.
tzselect can now use current time to help infer timezone.
The code now defaults to C99 or later.
Fix use of C23 attributes.
Changes to future timestamps
Starting in 2023, Egypt will observe DST from April's last Friday
through October's last Thursday. (Thanks to Ahmad ElDardiry.)
Assume the transition times are 00:00 and 24:00, respectively.
In 2023 Morocco's spring-forward transition after Ramadan
will occur April 23, not April 30. (Thanks to Milamber.)
Adjust predictions for future years accordingly. This affects
predictions for 2023, 2031, 2038, and later years.
This year Palestine will delay its spring forward from
March 25 to April 29 due to Ramadan. (Thanks to Heba Hamad.)
Make guesses for future Ramadans too.
Much of Greenland, represented by America/Nuuk, will continue to
observe DST using European Union rules. When combined with
Greenland's decision not to change the clocks in fall 2023,
America/Nuuk therefore changes from -03/-02 to -02/-01 effective
2023-10-29 at 01:00 UTC. (Thanks to Thomas M. Steenholdt.)
This change from 2022g doesn't affect timestamps until 2024-03-30,
and doesn't affect tm_isdst until 2023-03-25.
Changes to past timestamps
America/Yellowknife has changed from a Zone to a backward
compatibility Link, as it no longer differs from America/Edmonton
since 1970. (Thanks to Almaz Mingaleev.) This affects some
pre-1948 timestamps. The old data are now in 'backzone'.
Changes to past time zone abbreviations
When observing Moscow time, Europe/Kirov and Europe/Volgograd now
use the abbreviations MSK/MSD instead of numeric abbreviations,
for consistency with other timezones observing Moscow time.
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 on
a mostly-C89 platform, compile with -DPORT_TO_C89; this should
work on C89 platforms that also support C99 'long long' and
perhaps a few other extensions to C89. To support C89 callers of
tzcode's library, compile with -DSUPPORT_C89; however, this could
trigger latent bugs in C99-or-later callers. The two new macros
are transitional aids planned to be removed in a future version
(say, in 2029), 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 there are plans to discontinue leap seconds by 2035.
Release 2022g - 2022-11-29 08:58:31 -0800
Briefly:
The northern edge of Chihuahua changes to US timekeeping.
Much of Greenland stops changing clocks after March 2023.
Fix some pre-1996 timestamps in northern Canada.
C89 is now deprecated; please use C99 or later.
Portability fixes for AIX, libintl, MS-Windows, musl, z/OS
In C code, use more C23 features if available.
C23 timegm now supported by default
Fixes for unlikely integer overflows
Changes to future timestamps
In the Mexican state of Chihuahua, the border strip near the US
will change to agree with nearby US locations on 2022-11-30.
The strip's western part, represented by Ciudad Juárez, switches
from -06 all year to -07/-06 with US DST rules, like El Paso, TX.
The eastern part, represented by Ojinaga, will observe US DST next
year, like Presidio, TX. (Thanks to Heitor David Pinto.)
A new Zone America/Ciudad_Juarez splits from America/Ojinaga.
Much of Greenland, represented by America/Nuuk, stops observing
winter time after March 2023, so its daylight saving time becomes
standard time. (Thanks to Jonas Nyrup and Jürgen Appel.)
Changes to past timestamps
Changes for pre-1996 northern Canada (thanks to Chris Walton):
Merge America/Iqaluit and America/Pangnirtung into the former,
with a backward compatibility link for the latter name.
There is no good evidence the two locations differ since 1970.
This change affects pre-1996 America/Pangnirtung timestamps.
Cambridge Bay, Inuvik, Iqaluit, Rankin Inlet, Resolute and
Yellowknife did not observe DST in 1965, and did observe DST
from 1972 through 1979.
Whitehorse moved from -09 to -08 on 1966-02-27, not 1967-05-28.
Colombia's 1993 fallback was 02-06 24:00, not 04-04 00:00.
(Thanks to Alois Treindl.)
Singapore's 1981-12-31 change was at 16:00 UTC (23:30 local time),
not 24:00 local time. (Thanks to Geoff Clare via Robert Elz.)
Changes to code
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 Đoàn Trần Công 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.
Changes to build procedure
New Makefile rule check_mild that skips checking whether Link
lines are in the file 'backward'. (Inspired by a suggestion from
Stephen Colebourne.)
Release 2022f - 2022-10-28 18:04:57 -0700
Briefly:
Mexico will no longer observe DST except near the US border.
Chihuahua moves to year-round -06 on 2022-10-30.
Fiji no longer observes DST.
Move links to 'backward'.
In vanguard form, GMT is now a Zone and Etc/GMT a link.
zic now supports links to links, and vanguard form uses this.
Simplify four Ontario zones.
Fix a Y2438 bug when reading TZif data.
Enable 64-bit time_t on 32-bit glibc platforms.
Omit large-file support when no longer needed.
In C code, use some C23 features if available.
Remove no-longer-needed workaround for Qt bug 53071.
Changes to future timestamps
Mexico will no longer observe DST after 2022, except for areas
near the US border that continue to observe US DST rules.
On 2022-10-30 at 02:00 the Mexican state of Chihuahua moves
from -07 (-06 with DST) to year-round -06, thus not changing
its clocks that day. The new law states that Chihuahua
near the US border no longer observes US DST.
(Thanks to gera for the heads-up about Chihuahua.)
Fiji will not observe DST in 2022/3. (Thanks to Shalvin Narayan.)
For now, assume DST is suspended indefinitely.
Changes to data
Move links to 'backward' to ease and simplify link maintenance.
This affects generated data only if you use 'make BACKWARD='.
GMT is now a Zone and Etc/GMT a link instead of vice versa,
as GMT is needed for leap second support whereas Etc/GMT is not.
However, this change exposes a bug in TZUpdater 2.3.2 so it is
present only in vanguard form for now.
Vanguard form now uses links to links, as zic now supports this.
Changes to past timestamps
Simplify four Ontario zones, as most of the post-1970 differences
seem to have been imaginary. (Problem reported by Chris Walton.)
Move America/Nipigon, America/Rainy_River, and America/Thunder_Bay
to 'backzone'; backward-compatibility links still work, albeit
with some different timestamps before November 2005.
Changes to code
zic now supports links to links regardless of input line order.
For example, if Australia/Sydney is a Zone, the lines
Link Australia/Canberra Australia/ACT
Link Australia/Sydney Australia/Canberra
now work correctly, even though the shell commands
ln Australia/Canberra Australia/ACT
ln Australia/Sydney Australia/Canberra
would fail because the first command attempts to use a link
Australia/Canberra that does not exist until after the second
command is executed. Previously, zic had unspecified behavior if
a Link line's target was another link, and zic often misbehaved if
a Link line's target was a later Link line.
Fix line number in zic's diagnostic for a link to a link.
Fix a bug that caused localtime to mishandle timestamps starting
in the year 2438 when reading data generated by 'zic -b fat' when
distant-future DST transitions occur at times given in standard
time or in UT, not the usual case of local time. This occurs when
the corresponding .zi Rule lines specify DST transitions with TO
columns of 'max' and AT columns that end in 's' or 'u'. The
number 2438 comes from the 32-bit limit in the year 2038, plus the
400-year Gregorian cycle. (Problem reported by Bradley White.)
On glibc 2.34 and later, which optionally supports 64-bit time_t
on platforms like x86 where time_t was traditionally 32 bits,
default time_t to 64 instead of 32 bits. This lets functions like
localtime support timestamps after the year 2038, and fixes
year-2038 problems in zic when accessing files dated after 2038.
To continue to limit time_t to 32 bits on these platforms, use
"make CFLAGS='-D_TIME_BITS=32'".
In C code, do not enable large-file support on platforms like AIX
and macOS that no longer need it now that tzcode does not use
off_t or related functions like 'stat'. Large-file support is
still enabled by default on GNU/Linux, as it is needed for 64-bit
time_t support.
In C code, prefer C23 keywords to pre-C23 macros for alignof,
bool, false, and true. Also, use the following C23 features if
available: __has_include, unreachable.
zic no longer works around Qt bug 53071, as the relevant Qt
releases have been out of support since 2019. This change affects
only fat TZif files, as thin files never had the workaround.
zdump no longer modifies the environ vector when compiled on
platforms lacking tm_zone or when compiled with -DUSE_LTZ=0.
This avoid undefined behavior on POSIX platforms.
Release 2022e - 2022-10-11 11:13:02 -0700
Briefly:
Jordan and Syria switch from +02/+03 with DST to year-round +03.
Changes to future timestamps
Jordan and Syria are abandoning the DST regime and are changing to
permanent +03, so they will not fall back from +03 to +02 on
2022-10-28. (Thanks to Steffen Thorsen and Issam Al-Zuwairi.)
Changes to past timestamps
On 1922-01-01 Tijuana adopted standard time at 00:00, not 01:00.
Changes to past time zone abbreviations and DST flags
The temporary advancement of clocks in central Mexico in summer
1931 is now treated as daylight saving time, instead of as two
changes to standard time.
Release 2022d - 2022-09-23 12:02:57 -0700
Briefly:
Palestine transitions are now Saturdays at 02:00.
Simplify three Ukraine zones into one.
Changes to future timestamps
Palestine now springs forward and falls back at 02:00 on the
first Saturday on or after March 24 and October 24, respectively.
This means 2022 falls back 10-29 at 02:00, not 10-28 at 01:00.
(Thanks to Heba Hamad.)
Changes to past timestamps
Simplify three Ukraine zones to one, since the post-1970
differences seem to have been imaginary. Move Europe/Uzhgorod and
Europe/Zaporozhye to 'backzone'; backward-compatibility links
still work, albeit with different timestamps before October 1991.
Release 2022c - 2022-08-15 17:47:18 -0700
Briefly:
Work around awk bug in FreeBSD, macOS, etc.
Improve tzselect on intercontinental Zones.
Changes to code
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.
Release 2022b - 2022-08-10 15:38:32 -0700
Briefly:
Chile's DST is delayed by a week in September 2022.
Iran no longer observes DST after 2022.
Rename Europe/Kiev to Europe/Kyiv.
New zic -R option
Vanguard form now uses %z.
Finish moving duplicate-since-1970 zones to 'backzone'.
New build option PACKRATLIST
New tailored_tarballs target, replacing rearguard_tarballs
Changes to future timestamps
Chile's 2022 DST start is delayed from September 4 to September 11.
(Thanks to Juan Correa.)
Iran plans to stop observing DST permanently, after it falls back
on 2022-09-21. (Thanks to Ali Mirjamali.)
Changes to past timestamps
Finish moving to 'backzone' the location-based zones whose
timestamps since 1970 are duplicates; adjust links accordingly.
This change ordinarily affects only pre-1970 timestamps, and with
the new PACKRATLIST option it does not affect any timestamps.
In this round the affected zones are Antarctica/Vostok,
Asia/Brunei, Asia/Kuala_Lumpur, Atlantic/Reykjavik,
Europe/Amsterdam, Europe/Copenhagen, Europe/Luxembourg,
Europe/Monaco, Europe/Oslo, Europe/Stockholm, Indian/Christmas,
Indian/Cocos, Indian/Kerguelen, Indian/Mahe, Indian/Reunion,
Pacific/Chuuk, Pacific/Funafuti, Pacific/Majuro, Pacific/Pohnpei,
Pacific/Wake and Pacific/Wallis, and the affected links are
Arctic/Longyearbyen, Atlantic/Jan_Mayen, Iceland, Pacific/Ponape,
Pacific/Truk, and Pacific/Yap.
From fall 1994 through fall 1995, Shanks wrote that Crimea's
DST transitions were at 02:00 standard time, not at 00:00.
(Thanks to Michael Deckers.)
Iran adopted standard time in 1935, not 1946. In 1977 it observed
DST from 03-21 23:00 to 10-20 24:00; its 1978 transitions were on
03-24 and 08-05, not 03-20 and 10-20; and its spring 1979
transition was on 05-27, not 03-21.
(Thanks to Roozbeh Pournader and Francis Santoni.)
Chile's observance of -04 from 1946-08-29 through 1947-03-31 was
considered DST, not standard time. Santiago and environs had moved
their clocks back to rejoin the rest of mainland Chile; put this
change at the end of 1946-08-28. (Thanks to Michael Deckers.)
Some old, small clock transitions have been removed, as people at
the time did not change their clocks. This affects Asia/Hong_Kong
in 1904, Asia/Ho_Chi_Minh in 1906, and Europe/Dublin in 1880.
Changes to zone name
Rename Europe/Kiev to Europe/Kyiv, as "Kyiv" is more common in
English now. Spelling of other names in Ukraine has not yet
demonstrably changed in common English practice so for now these
names retain old spellings, as in other countries (e.g.,
Europe/Prague not "Praha", and Europe/Sofia not "Sofiya").
Changes to code
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 simultaneously with the first DST fallback transition.
Changes to build procedure
Source data in vanguard form now uses the %z notation, introduced
in release 2015f. For example, for America/Sao_Paulo vanguard
form contains the zone continuation line "-3:00 Brazil %z", which
is simpler and more reliable than the line "-3:00 Brazil -03/-02"
used in main and rearguard forms. The plan is for the main form
to use %z eventually; in the meantime maintainers of zi parsers
are encouraged to test the parsers on vanguard.zi.
The Makefile has a new PACKRATLIST option to select a subset of
'backzone'. For example, 'make PACKRATDATA=backzone
PACKRATLIST=zone.tab' now generates TZif files identical to those
of the global-tz project.
The Makefile has a new tailored_tarballs target for generating
special-purpose tarballs. It generalizes and replaces the
rearguard_tarballs target and related targets and macros, which
are now obsolescent.
'make install' now defaults LOCALTIME to Factory not GMT,
which means the default abbreviation is now "-00" not "GMT".
Remove the posix_packrat target, marked obsolescent in 2016a.
Release 2022a - 2022-03-15 23:02:01 -0700
Briefly:
Palestine will spring forward on 2022-03-27, not -03-26.
zdump -v now outputs better failure indications.
Bug fixes for code that reads corrupted TZif data.
Changes to future timestamps
Palestine will spring forward on 2022-03-27, not 2022-03-26.
(Thanks to Heba Hamad.) Predict future transitions for first
Sunday >= March 25. Additionally, predict fallbacks to be the first
Friday on or after October 23, not October's last Friday, to be more
consistent with recent practice. The first differing fallback
prediction is on 2025-10-24, not 2025-10-31.
Changes to past timestamps
From 1992 through spring 1996, Ukraine's DST transitions were at
02:00 standard time, not at 01:00 UTC. (Thanks to Alois Treindl.)
Chile's Santiago Mean Time and its LMT precursor have been adjusted
eastward by 1 second to align with past and present law.
Changes to commentary
Add several references for Chile's 1946/1947 transitions, some of
which only affected portions of the country.
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.
Changes to build procedure
Distribution tarballs now use standard POSIX.1-1988 ustar format
instead of GNU format. Although the formats are almost identical
for these tarballs, ustar headers' magic fields contain "ustar"
instead of "ustar ", and their version fields contain "00" instead
of " ". The two formats are planned to diverge more significantly
for tzdb releases after 2242-03-16 12:56:31 UTC, when the ustar
format becomes obsolete and the tarballs switch to pax format, an
extension of ustar. For details about these formats, please see
"pax - portable archive interchange", IEEE Std 1003.1-2017,
<https://pubs.opengroup.org/onlinepubs/9699919799/utilities/pax.html#tag_20_92_13>.
Release 2021e - 2021-10-21 18:41:00 -0700
Changes to future timestamps
Palestine will fall back 10-29 (not 10-30) at 01:00.
(Thanks to P Chan and Heba Hemad.)
Release 2021d - 2021-10-15 13:48:18 -0700
Briefly:
Fiji suspends DST for the 2021/2022 season.
'zic -r' marks unspecified timestamps with "-00".
Changes to future timestamps
Fiji will suspend observance of DST for the 2021/2022 season.
Assume for now that it will return next year. (Thanks to Jashneel
Kumar and P Chan.)
Changes to code
'zic -r' now uses "-00" time zone abbreviations for intervals
with UT offsets that are unspecified due to -r truncation.
This implements a change in draft Internet RFC 8536bis.
Release 2021c - 2021-10-01 14:21:49 -0700
Briefly:
Revert most 2021b changes to 'backward'.
Fix 'zic -b fat' bug in pre-1970 32-bit data.
Fix two Link line typos.
Distribute SECURITY file.
This release is intended as a bugfix release, to fix compatibility
problems and typos reported since 2021b was released.
Changes to Link directives
Revert almost all of 2021b's changes to the 'backward' file,
by moving Link directives back to where they were in 2021a.
Although 'zic' doesn't care which source file contains a Link
directive, some downstream uses ran into trouble with the move.
(Problem reported by Stephen Colebourne for Joda-Time.)
Fix typo that linked Atlantic/Jan_Mayen to the wrong location
(problem reported by Chris Walton).
Fix 'backzone' typo that linked America/Virgin to the wrong
location (problem reported by Michael Deckers).
Changes to code
Fix a bug in 'zic -b fat' that caused old timestamps to be
mishandled in 32-bit-only readers (problem reported by Daniel
Fischer).
Changes to documentation
Distribute the SECURITY file (problem reported by Andreas Radke).
Release 2021b - 2021-09-24 16:23:00 -0700
Briefly:
Jordan now starts DST on February's last Thursday.
Samoa no longer observes DST.
Merge more location-based Zones whose timestamps agree since 1970.
Move some backward-compatibility links to 'backward'.
Rename Pacific/Enderbury to Pacific/Kanton.
Correct many pre-1993 transitions in Malawi, Portugal, etc.
zic now creates each output file or link atomically.
zic -L no longer omits the POSIX TZ string in its output.
zic fixes for truncation and leap second table expiration.
zic now follows POSIX for TZ strings using all-year DST.
Fix some localtime crashes and bugs in obscure cases.
zdump -v now outputs more-useful boundary cases.
tzfile.5 better matches a draft successor to RFC 8536.
A new file SECURITY.
This release is prompted by recent announcements by Jordan and Samoa.
It incorporates many other changes that had accumulated since 2021a.
However, it omits most proposed changes that merged all Zones
agreeing since 1970, as concerns were raised about doing too many of
these changes at once. It does keeps some of these changes in the
interest of making tzdb more equitable one step at a time; see
"Merge more location-based Zones" below.
Changes to future timestamps
Jordan now starts DST on February's last Thursday.
(Thanks to Steffen Thorsen.)
Samoa no longer observes DST. (Thanks to Geoffrey D. Bennett.)
Changes to zone name
Rename Pacific/Enderbury to Pacific/Kanton. When we added
Enderbury in 1993, we did not know that it is uninhabited and that
Kanton (population two dozen) is the only inhabited location in
that timezone. The old name is now a backward-compatibility link.
Changes to past timestamps
Correct many pre-1993 transitions, fixing entries originally
derived from Shanks, Whitman, and Mundell. The fixes include:
- Barbados: standard time was introduced in 1911, not 1932; and
DST was observed in 1942-1944
- Cook Islands: In 1899 they switched from east to west of GMT,
celebrating Christmas for two days. They (and Niue) switched
to standard time in 1952, not 1901.
- Guyana: corrected LMT for Georgetown; the introduction of
standard time in 1911, not 1915; and corrections to 1975 and
1992 transitions
- Kanton: uninhabited before 1937-08-31
- Niue: only observed -11:20 from 1952 through 1964, then went to
-11 instead of -11:30
- Portugal: DST was observed in 1950
- Tonga: corrected LMT; the introduction of standard time in 1945,
not 1901; and corrections to the transition from +12:20 to +13
in 1961, not 1941
Additional fixes to entries in the 'backzone' file include:
- Enderbury: inhabited only 1860/1885 and 1938-03-06/1942-02-09
- The Gambia: 1933 and 1942 transitions
- Malawi: several 1911 through 1925 transitions
- Sierra Leone: several 1913 through 1941 transitions, and DST
was NOT observed in 1957 through 1962
(Thanks to P Chan, Michael Deckers, Alexander Krivenyshev and
Alois Treindl.)
Merge more location-based Zones whose timestamps agree since 1970,
as pre-1970 timestamps are out of scope. This is part of a
process that has been ongoing since 2013. This does not affect
post-1970 timestamps, and timezone historians who build with 'make
PACKRATDATA=backzone' should see no changes to pre-1970 timestamps.
When merging, keep the most-populous location's data, and move
data for other locations to 'backzone' with a backward
link in 'backward'. For example, move America/Creston data to
'backzone' with a link in 'backward' from America/Phoenix because
the two timezones' timestamps agree since 1970; this change
affects some pre-1968 timestamps in America/Creston because
Creston and Phoenix disagreed before 1968. The affected Zones
are Africa/Accra, America/Atikokan, America/Blanc-Sablon,
America/Creston, America/Curacao, America/Nassau,
America/Port_of_Spain, Antarctica/DumontDUrville, and
Antarctica/Syowa.
Changes to maintenance procedure
The new file SECURITY covers how to report security-related bugs.
Several backward-compatibility links have been moved to the
'backward' file. These links, which range from Africa/Addis_Ababa
to Pacific/Saipan, are only for compatibility with now-obsolete
guidelines suggesting an entry for every ISO 3166 code.
The intercontinental convenience links Asia/Istanbul and
Europe/Nicosia have also been moved to 'backward'.
Changes to code
zic now creates each output file or link atomically,
possibly by creating a temporary file and then renaming it.
This avoids races where a TZ setting would temporarily stop
working while zic was installing a replacement file or link.
zic -L no longer omits the POSIX TZ string in its output.
Starting with 2020a, zic -L truncated its output according to the
"Expires" directive or "#expires" comment in the leapseconds file.
The resulting TZif files omitted daylight saving transitions after
the leap second table expired, which led to far less accurate
predictions of times after the expiry. Although future timestamps
cannot be converted accurately in the presence of leap seconds, it
is more accurate to convert near-future timestamps with a few
seconds error than with an hour error, so zic -L no longer
truncates output in this way.
Instead, when zic -L is given the "Expires" directive, it now
outputs the expiration by appending a no-change entry to the leap
second table. Although this should work well with most TZif
readers, it does not conform to Internet RFC 8536 and some pickier
clients (including tzdb 2017c through 2021a) reject it, so
"Expires" directives are currently disabled by default. To enable
them, set the EXPIRES_LINE Makefile variable. If a TZif file uses
this new feature it is marked with a new TZif version number 4,
a format intended to be documented in a successor to RFC 8536.
The old-format "#expires" comments are now treated solely as
comments and have no effect on the TZif files.
zic -L LEAPFILE -r @LO no longer generates an invalid TZif file
that omits leap second information for the range LO..B when LO
falls between two leap seconds A and B. Instead, it generates a
TZif version 4 file that represents the previously missing
information.
The TZif reader now allows the leap second table to begin with a
correction other than -1 or +1, and to contain adjacent
transitions with equal corrections. This supports TZif version 4.
The TZif reader now lets leap seconds occur less than 28 days
apart. This supports possible future TZif extensions.
Fix bug that caused 'localtime' etc. to crash when TZ was
set to a all-year DST string like "EST5EDT4,0/0,J365/25" that does
not conform to POSIX but does conform to Internet RFC 8536.
Fix another bug that caused 'localtime' etc. to crash when TZ was
set to a POSIX-conforming but unusual TZ string like
"EST5EDT4,0/0,J365/0", where almost all the year is DST.
Fix yet another bug that caused 'localtime' etc. to mishandle slim
TZif files containing leap seconds after the last explicit
transition in the table, or when handling far-future timestamps