2024.2: Release of upstream tzdata 2024b

Version 2024.2

Upstream version 2024b released 2024-09-04T19:27:47+00:00

Briefly:

Improve historical data for Mexico, Mongolia, and Portugal. 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. SUPPORT_C89 now
defaults to 1.

Changes to past timestamps

Asia/Choibalsan is now an alias for Asia/Ulaanbaatar rather than being a
separate Zone with differing behavior before April 2008. This seems better given
our wildly conflicting information about Mongolia's time zone history. (Thanks
to Heitor David Pinto.)

Historical transitions for Mexico have been updated based on official Mexican
decrees. The affected timestamps occur during the years 1921-1927, 1931, 1945,
1949-1970, and 1981-1997. The affected zones are America/Bahia_Banderas,
America/Cancun, America/Chihuahua, America/Ciudad_Juarez, America/Hermosillo,
America/Mazatlan, America/Merida, America/Mexico_City, America/Monterrey,
America/Ojinaga, and America/Tijuana. (Thanks to Heitor David Pinto.)

Historical transitions for Portugal, represented by Europe/Lisbon,
Atlantic/Azores, and Atlantic/Madeira, have been updated based on a close
reading of old Portuguese legislation, replacing previous data mainly
originating from Whitman and Shanks & Pottenger. These changes affect a few
transitions in 1917-1921, 1924, and 1940 throughout these regions by a few hours
or days, and various timestamps between 1977 and 1993 depending on the region.
In particular, the Azores and Madeira did not observe DST from 1977 to 1981.
Additionally, the adoption of standard zonal time in former Portuguese colonies
have been adjusted: Africa/Maputo in 1909, and Asia/Dili by 22 minutes at the
start of 1912. (Thanks to Tim Parenti.)

Changes to past tm_isdst flags

The period from 1966-04-03 through 1966-10-02 in Portugal is now modeled as DST,
to more closely reflect how contemporaneous changes in law entered into force.

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.

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 documentation

The documentation now reflects POSIX.1-2024.

Changes to commentary

Commentary about historical transitions in Portugal and her former colonies has
been expanded with links to many relevant legislation. (Thanks to Tim Parenti.)

2024.1: Release of upstream tzdata 2024a

Version 2024.1

Upstream version 2024a released 2024-02-01T17:28:56+00:00

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 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.)

2023.4: Release of upstream tzdata 2023d

Version 2023.4

Upstream version 2023d released 2023-12-22T04:02:24+00:00

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 commentary

Limitations and hazards of the optional support for obsolescent C89 platforms
are documented better, along with a tentative schedule for removing this
support.

2023.3: Release of upstream tzdata 2023c

Version 2023.3

Upstream version 2023c released 2023-03-28T19:42:14+00:00

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.)

2023.2: Release of upstream tzdata 2023b

Version 2023.2

Upstream version 2023b released 2023-03-24T02:50:38+00:00

Briefly:

Lebanon delays the start of DST this year.

Changes to future timestamps

This year Lebanon springs forward April 20/21 not March 25/26. (Thanks to
Saadallah Itani.)

2023.1: Release of upstream tzdata 2023a

Version 2023.1

Upstream version 2023a released 2023-03-22T19:39:33+00:00

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 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.

2022.7: Release of upstream tzdata 2022g

Version 2022.7

Upstream version 2022g released 2022-11-29T16:58:31+00:00

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.)

2022.6: Release of upstream tzdata 2022f

Version 2022.6

Upstream version 2022f released 2022-10-29T01:04:57+00:00

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.

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.

2022.5: Release of upstream tzdata 2022e

Version 2022.5

Upstream version 2022e released 2022-10-11T18:13:02+00:00

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.

2022.4: Release of upstream tzdata 2022d

Version 2022.4

Upstream version 2022d released 2022-09-23T19:02:57+00:00

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.