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NEWS
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News for the tz database
Unreleased, experimental changes
Briefly:
Egypt now uses DST again, from April through October.
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.
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.
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.
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.
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.
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
in slim TZif files lacking leap seconds.
Fix localtime misbehavior involving positive leap seconds.
This change affects only behavior for "right" system time,
which contains leap seconds, and only if the UT offset is
not a multiple of 60 seconds when a positive leap second occurs.
(No such timezone exists in tzdb, luckily.) Without the fix,
the timestamp was ambiguous during a positive leap second.
With the fix, any seconds occurring after a positive leap second
and within the same localtime minute are counted through 60, not
through 59; their UT offset (tm_gmtoff) is the same as before.
Here is how the fix affects timestamps in a timezone with UT
offset +01:23:45 (5025 seconds) and with a positive leap second at
1972-06-30 23:59:60 UTC (78796800):
time_t without the fix with the fix
78796800 1972-07-01 01:23:45 1972-07-01 01:23:45 (leap second)
78796801 1972-07-01 01:23:45 1972-07-01 01:23:46
...
78796815 1972-07-01 01:23:59 1972-07-01 01:23:60
78796816 1972-07-01 01:24:00 1972-07-01 01:24:00
Fix an unlikely bug that caused 'localtime' etc. to misbehave if
civil time changes a few seconds before time_t wraps around, when
leap seconds are enabled.
Fix bug in zic -r; in some cases, the dummy time type after the
last time transition disagreed with the TZ string, contrary to
Internet RFC 8563 section 3.3.
Fix a bug with 'zic -r @X' when X is a negative leap second that
has a nonnegative correction. Without the fix, the output file
was truncated so that X appeared to be a positive leap second.
Fix a similar, even less likely bug when truncating at a positive
leap second that has a nonpositive correction.
zic -r now reports an error if given rolling leap seconds, as this
usage has never generally worked and is evidently unused.
zic now generates a POSIX-conforming TZ string for TZif files
where all-year DST is predicted for the indefinite future.
For example, for all-year Eastern Daylight Time, zic now generates
"XXX3EDT4,0/0,J365/23" where it previously generated
"EST5EDT,0/0,J365/25" or "". (Thanks to Michael Deckers for
noting the possibility of POSIX conformance.)
zic.c no longer requires sys/wait.h (thanks to spazmodius for
noting it wasn't needed).
When reading slim TZif files, zdump no longer mishandles leap
seconds on the rare platforms where time_t counts leap seconds,
fixing a bug introduced in 2014g.
zdump -v now outputs timestamps at boundaries of what localtime
and gmtime can represent, instead of the less useful timestamps
one day after the minimum and one day before the maximum.
(Thanks to Arthur David Olson for prototype code, and to Manuela
Friedrich for debugging help.)
zdump's -c and -t options are now consistently inclusive for the
lower time bound and exclusive for the upper. Formerly they were
inconsistent. (Confusion noted by Martin Burnicki.)
Changes to build procedure
You can now compile with -DHAVE_MALLOC_ERRNO=0 to port to
non-POSIX hosts where malloc doesn't set errno.
(Problem reported by Jan Engelhardt.)
Changes to documentation
tzfile.5 better matches a draft successor to RFC 8536
<https://datatracker.ietf.org/doc/draft-murchison-rfc8536bis/01/>.
Release 2021a - 2021-01-24 10:54:57 -0800
Changes to future timestamps
South Sudan changes from +03 to +02 on 2021-02-01 at 00:00.
(Thanks to Steffen Thorsen.)
Release 2020f - 2020-12-29 00:17:46 -0800
Change to build procedure
'make rearguard_tarballs' no longer generates a bad rearguard.zi,
fixing a 2020e bug. (Problem reported by Deborah Goldsmith.)
Release 2020e - 2020-12-22 15:14:34 -0800
Briefly:
Volgograd switches to Moscow time on 2020-12-27 at 02:00.
Changes to future timestamps
Volgograd changes time zone from +04 to +03 on 2020-12-27 at 02:00.
(Thanks to Alexander Krivenyshev and Stepan Golosunov.)
Changes to past timestamps
Correct many pre-1986 transitions, fixing entries originally
derived from Shanks. The fixes include:
- Australia: several 1917 through 1971 transitions
- The Bahamas: several 1941 through 1945 transitions
- Bermuda: several 1917 through 1956 transitions
- Belize: several 1942 through 1968 transitions
- Ghana: several 1915 through 1956 transitions
- Israel and Palestine: several 1940 through 1985 transitions
- Kenya and adjacent: several 1908 through 1960 transitions
- Nigeria and adjacent: correcting LMT in Lagos, and several 1905
through 1919 transitions
- Seychelles: the introduction of standard time in 1907, not 1906
- Vanuatu: DST in 1973-1974, and a corrected 1984 transition
(Thanks to P Chan.)
Because of the Australia change, Australia/Currie (King Island) is
no longer needed, as it is identical to Australia/Hobart for all
timestamps since 1970 and was therefore created by mistake.
Australia/Currie has been moved to the 'backward' file and its
corrected data moved to the 'backzone' file.
Changes to past time zone abbreviations and DST flags
To better match legislation in Turks and Caicos, the 2015 shift to
year-round observance of -04 is now modeled as AST throughout before
returning to Eastern Time with US DST in 2018, rather than as
maintaining EDT until 2015-11-01. (Thanks to P Chan.)
Changes to documentation
The zic man page now documents zic's coalescing of transitions
when a zone falls back just before DST springs forward.
Release 2020d - 2020-10-21 11:24:13 -0700
Briefly:
Palestine ends DST earlier than predicted, on 2020-10-24.
Changes to past and future timestamps
Palestine ends DST on 2020-10-24 at 01:00, instead of 2020-10-31
as previously predicted (thanks to Sharef Mustafa.) Its
2019-10-26 fall-back was at 00:00, not 01:00 (thanks to Steffen
Thorsen.) Its 2015-10-23 transition was at 01:00 not 00:00, and
its spring 2020 transition was on March 28 at 00:00, not March 27
(thanks to Pierre Cashon.) This affects Asia/Gaza and
Asia/Hebron. Assume future spring and fall transitions will be on
the Saturday preceding the last Sunday of March and October,
respectively.
Release 2020c - 2020-10-16 11:15:53 -0700
Briefly:
Fiji starts DST later than usual, on 2020-12-20.
Changes to future timestamps
Fiji will start DST on 2020-12-20, instead of 2020-11-08 as
previously predicted. DST will still end on 2021-01-17.
(Thanks to Raymond Kumar and Alan Mintz.) Assume for now that
the later-than-usual start date is a one-time departure from the
recent pattern.
Changes to build procedure
Rearguard tarballs now contain an empty file pacificnew.
Some older downstream software expects this file to exist.
(Problem reported by Mike Cullinan.)
Release 2020b - 2020-10-06 18:35:04 -0700
Briefly:
Revised predictions for Morocco's changes starting in 2023.
Canada's Yukon changes to -07 on 2020-11-01, not 2020-03-08.
Macquarie Island has stayed in sync with Tasmania since 2011.
Casey, Antarctica is at +08 in winter and +11 in summer.
zic no longer supports -y, nor the TYPE field of Rules.
Changes to future timestamps
Morocco's spring-forward after Ramadan is now predicted to occur
no sooner than two days after Ramadan, instead of one day.
(Thanks to Milamber.) The first altered prediction is for 2023,
now predicted to spring-forward on April 30 instead of April 23.
Changes to past and future timestamps
Casey Station, Antarctica has been using +08 in winter and +11 in
summer since 2018. The most recent transition from +08 to +11 was
2020-10-04 00:01. Also, Macquarie Island has been staying in
sync with Tasmania since 2011. (Thanks to Steffen Thorsen.)
Changes to past and future time zone abbreviations and DST flags
Canada's Yukon, represented by America/Whitehorse and
America/Dawson, changes its time zone rules from -08/-07 to
permanent -07 on 2020-11-01, not on 2020-03-08 as 2020a had it.
This change affects only the time zone abbreviation (MST vs PDT)
and daylight saving flag for the period between the two dates.
(Thanks to Andrew G. Smith.)
Changes to past timestamps
Correct several transitions for Hungary for 1918/1983.
For example, the 1983-09-25 fall-back was at 01:00, not 03:00.
(Thanks to Géza Nyáry.) Also, the 1890 transition to standard
time was on 11-01, not 10-01 (thanks to Michael Deckers).
The 1891 French transition was on March 16, not March 15. The
1911-03-11 French transition was at midnight, not a minute later.
Monaco's transitions were on 1892-06-01 and 1911-03-29, not
1891-03-15 and 1911-03-11. (Thanks to Michael Deckers.)
Changes to code
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.
Changes to build procedure
The Makefile now defaults POSIXRULES to '-', so the posixrules
feature (obsolete as of 2019b) is no longer installed by default.
Changes to documentation and commentary
The long-obsolete files pacificnew, systemv, and yearistype.sh have
been removed from the distribution. (Thanks to Tim Parenti.)
Release 2020a - 2020-04-23 16:03:47 -0700
Briefly:
Morocco springs forward on 2020-05-31, not 2020-05-24.
Canada's Yukon advanced to -07 year-round on 2020-03-08.
America/Nuuk renamed from America/Godthab.
zic now supports expiration dates for leap second lists.
Changes to future timestamps
Morocco's second spring-forward transition in 2020 will be May 31,
not May 24 as predicted earlier. (Thanks to Semlali Naoufal.)
Adjust future-year predictions to use the first Sunday after the
day after Ramadan, not the first Sunday after Ramadan.
Canada's Yukon, represented by America/Whitehorse and
America/Dawson, advanced to -07 year-round, beginning with its
spring-forward transition on 2020-03-08, and will not fall back on
2020-11-01. Although a government press release calls this
"permanent Pacific Daylight Saving Time", we prefer MST for
consistency with nearby Dawson Creek, Creston, and Fort Nelson.
(Thanks to Tim Parenti.)
Changes to past timestamps
Shanghai observed DST in 1919. (Thanks to Phake Nick.)
Changes to timezone identifiers
To reflect current usage in English better, America/Godthab has
been renamed to America/Nuuk. A backwards-compatibility link
remains for the old name.
Changes to code
localtime.c no longer mishandles timestamps after the last
transition in a TZif file with leap seconds and with daylight
saving time transitions projected into the indefinite future.
For example, with TZ='America/Los_Angeles' with leap seconds,
zdump formerly reported a DST transition on 2038-03-14
from 01:59:32.999... to 02:59:33 instead of the correct transition