Tzdata

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.)

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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.)

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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.

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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.)

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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.)

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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.

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