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News for the tz database
Release 2019c - 2019-09-11 08:59:48 -0700
Briefly:
Fiji observes DST from 2019-11-10 to 2020-01-12.
Norfolk Island starts observing Australian-style DST.
Changes to future timestamps
Fiji's next DST transitions will be 2019-11-10 and 2020-01-12
instead of 2019-11-03 and 2020-01-19. (Thanks to Raymond Kumar.)
Adjust future guesses accordingly.
Norfolk Island will observe Australian-style DST starting in
spring 2019. The first transition is on 2019-10-06. (Thanks to
Kyle Czech and Michael Deckers.)
Changes to past timestamps
Many corrections to time in Turkey from 1940 through 1985.
(Thanks to Oya Vulaş via Alois Treindl, and to Kıvanç Yazan.)
The Norfolk Island 1975-03-02 transition was at 02:00 standard
time, not 02:00 DST. (Thanks to Michael Deckers.)
South Korea observed DST from 1948 through 1951. Although this
info was supposed to appear in release 2014j, a typo inadvertently
suppressed the change. (Thanks to Alois Treindl.)
Detroit observed DST in 1967 and 1968 following the US DST rules,
except that its 1967 DST began on June 14 at 00:01. (Thanks to
Alois Treindl for pointing out that the old data entries were
probably wrong.)
Fix several errors in pre-1970 transitions in Perry County, IN.
(Thanks to Alois Triendl for pointing out the 1967/9 errors.)
Edmonton did not observe DST in 1967 or 1969. In 1946 Vancouver
ended DST on 09-29 not 10-13, and Vienna ended DST on 10-07 not
10-06. In 1945 Königsberg (now Kaliningrad) switched from +01/+02
to +02/+03 on 04-10 not 01-01, and its +02/+03 is abbreviated
EET/EEST, not CET/CEST. (Thanks to Alois Triendl.) In 1946
Königsberg switched to +03 on 04-07 not 01-01.
In 1946 Louisville switched from CST to CDT on 04-28 at 00:01, not
01-01 at 00:00. (Thanks to Alois Treindl and Michael Deckers.)
Also, it switched from CST to CDT on 1950-04-30, not 1947-04-27.
The 1892-05-01 transition in Brussels was at 00:17:30, not at noon.
(Thanks to Michael Deckers.)
Changes to past time zone abbreviations and DST flags
Hong Kong Winter Time, observed from 1941-10-01 to 1941-12-25,
is now flagged as DST and is abbreviated HKWT not HKT.
Changes to code
leapseconds.awk now relies only on its input data, rather than
also relying on its comments. (Inspired by code from Dennis
Ferguson and Chris Woodbury.)
The code now defends against CRLFs in leap-seconds.list.
(Thanks to Brian Inglis and Chris Woodbury.)
Changes to documentation and commentary
theory.html discusses leap seconds. (Thanks to Steve Summit.)
Nashville's newspapers dueled about the time of day in the 1950s.
(Thanks to John Seigenthaler.)
Liechtenstein observed Swiss DST in 1941/2.
(Thanks to Alois Treindl.)
Release 2019b - 2019-07-01 00:09:53 -0700
Briefly:
Brazil no longer observes DST.
'zic -b slim' outputs smaller TZif files; please try it out.
Palestine's 2019 spring-forward transition was on 03-29, not 03-30.
Changes to future timestamps
Brazil has canceled DST and will stay on standard time indefinitely.
(Thanks to Steffen Thorsen, Marcus Diniz, and Daniel Soares de
Oliveira.)
Predictions for Morocco now go through 2087 instead of 2037, to
work around a problem on newlib when using TZif files output by
zic 2019a or earlier. (Problem reported by David Gauchard.)
Changes to past and future timestamps
Palestine's 2019 spring transition was 03-29 at 00:00, not 03-30
at 01:00. (Thanks to Sharef Mustafa and Even Scharning.) Guess
future transitions to be March's last Friday at 00:00.
Changes to past timestamps
Hong Kong's 1941-06-15 spring-forward transition was at 03:00, not
03:30. Its 1945 transition from JST to HKT was on 11-18 at 02:00,
not 09-15 at 00:00. In 1946 its spring-forward transition was on
04-21 at 00:00, not the previous day at 03:30. From 1946 through
1952 its fall-back transitions occurred at 04:30, not at 03:30.
In 1947 its fall-back transition was on 11-30, not 12-30.
(Thanks to P Chan.)
Changes to past time zone abbreviations
Italy's 1866 transition to Rome Mean Time was on December 12, not
September 22. This affects only the time zone abbreviation for
Europe/Rome between those dates. (Thanks to Stephen Trainor and
Luigi Rosa.)
Changes affecting metadata only
Add info about the Crimea situation in zone1970.tab and zone.tab.
(Problem reported by Serhii Demediuk.)
Changes to code
zic's new -b option supports a way to control data bloat and to
test for year-2038 bugs in software that reads TZif files.
'zic -b fat' and 'zic -b slim' generate larger and smaller output;
for example, changing from fat to slim shrinks the Europe/London
file from 3648 to 1599 bytes, saving about 56%. Fat and slim
files represent the same set of timestamps and use the same TZif
format as documented in tzfile(5) and in Internet RFC 8536.
Fat format attempts to work around bugs or incompatibilities in
older software, notably software that mishandles 64-bit TZif data
or uses obsolete TZ strings like "EET-2EEST" that lack DST rules.
Slim format is more efficient and does not work around 64-bit bugs
or obsolete TZ strings. Currently zic defaults to fat format
unless you compile with -DZIC_BLOAT_DEFAULT=\"slim\"; this
out-of-the-box default is intended to change in future releases
as the buggy software often mishandles timestamps anyway.
zic no longer treats a set of rules ending in 2037 specially.
Previously, zic assumed that such a ruleset meant that future
timestamps could not be predicted, and therefore omitted a
POSIX-like TZ string in the TZif output. The old behavior is no
longer needed for current tzdata, and caused problems with newlib
when used with older tzdata (reported by David Gauchard).
zic no longer generates some artifact transitions. For example,
Europe/London no longer has a no-op transition in January 1996.
Changes to build procedure
tzdata.zi now assumes zic 2017c or later. This shrinks tzdata.zi
by a percent or so.
Changes to documentation and commentary
The Makefile now documents the POSIXRULES macro as being obsolete,
and similarly, zic's -p POSIXRULES option is now documented as
being obsolete. Although the POSIXRULES feature still exists and
works as before, in practice it is rarely used for its intended
purpose, and it does not work either in the default reference
implementation (for timestamps after 2037) or in common
implementations such as GNU/Linux (for contemporary timestamps).
Since POSIXRULES was designed primarily as a temporary transition
facility for System V platforms that died off decades ago, it is
being decommissioned rather than institutionalized.
New info on Bonin Islands and Marcus (thanks to Wakaba and Phake Nick).
Release 2019a - 2019-03-25 22:01:33 -0700
Briefly:
Palestine "springs forward" on 2019-03-30 instead of 2019-03-23.
Metlakatla "fell back" to rejoin Alaska Time on 2019-01-20 at 02:00.
Changes to past and future timestamps
Palestine will not start DST until 2019-03-30, instead of 2019-03-23 as
previously predicted. Adjust our prediction by guessing that spring
transitions will be between 24 and 30 March, which matches recent practice
since 2016. (Thanks to Even Scharning and Tim Parenti.)
Metlakatla ended its observance of Pacific standard time,
rejoining Alaska Time, on 2019-01-20 at 02:00. (Thanks to Ryan
Stanley and Tim Parenti.)
Changes to past timestamps
Israel observed DST in 1980 (08-02/09-13) and 1984 (05-05/08-25).
(Thanks to Alois Treindl and Isaac Starkman.)
Changes to time zone abbreviations
Etc/UCT is now a backward-compatibility link to Etc/UTC, instead
of being a separate zone that generates the abbreviation "UCT",
which nowadays is typically a typo. (Problem reported by Isiah
Meadows.)
Changes to code
zic now has an -r option to limit the time range of output data.
For example, 'zic -r @1000000000' limits the output data to
timestamps starting 1000000000 seconds after the Epoch.
This helps shrink output size and can be useful for applications
not needing the full timestamp history, such as TZDIST truncation;
see Internet RFC 8536 section 5.1. (Inspired by a feature request
from Christopher Wong, helped along by bug reports from Wong and
from Tim Parenti.)
Changes to documentation
Mention Internet RFC 8536 (February 2019), which documents TZif.
tz-link.html now cites tzdata-meta
<https://tzdata-meta.timtimeonline.com/>.
Release 2018i - 2018-12-30 11:05:43 -0800
Briefly:
São Tomé and Príncipe switches from +01 to +00 on 2019-01-01.
Changes to future timestamps
Due to a change in government, São Tomé and Príncipe switches back
from +01 to +00 on 2019-01-01 at 02:00. (Thanks to Vadim
Nasardinov and Michael Deckers.)
Release 2018h - 2018-12-23 17:59:32 -0800
Briefly:
Qyzylorda, Kazakhstan moved from +06 to +05 on 2018-12-21.
New zone Asia/Qostanay because Qostanay, Kazakhstan didn't move.
Metlakatla, Alaska observes PST this winter only.
Guess Morocco will continue to adjust clocks around Ramadan.
Add predictions for Iran from 2038 through 2090.
Changes to future timestamps
Guess that Morocco will continue to fall back just before and
spring forward just after Ramadan, the practice since 2012.
(Thanks to Maamar Abdelkader.) This means Morocco will observe
negative DST during Ramadan in main and vanguard formats, and in
rearguard format it stays in the +00 timezone and observes
ordinary DST in all months other than Ramadan. As before, extend
this guesswork to the year 2037. As a consequence, Morocco is
scheduled to observe three DST transitions in some Gregorian years
(e.g., 2033) due to the mismatch between the Gregorian and Islamic
calendars.
The table of exact transitions for Iranian DST has been extended.
It formerly cut off before the year 2038 in a nod to 32-bit time_t.
It now cuts off before 2091 as there is doubt about how the Persian
calendar will treat 2091. This change predicts DST transitions in
2038-9, 2042-3, and 2046-7 to occur one day later than previously
predicted. As before, post-cutoff transitions are approximated.
Changes to past and future timestamps
Qyzylorda (aka Kyzylorda) oblast in Kazakhstan moved from +06 to
+05 on 2018-12-21. This is a zone split as Qostanay (aka
Kostanay) did not switch, so create a zone Asia/Qostanay.
Metlakatla moved from Alaska to Pacific standard time on 2018-11-04.
It did not change clocks that day and remains on -08 this winter.
(Thanks to Ryan Stanley.) It will revert to the usual Alaska
rules next spring, so this change affects only timestamps
from 2018-11-04 through 2019-03-10.
Change to past timestamps
Kwajalein's 1993-08-20 transition from -12 to +12 was at 24:00,
not 00:00. I transcribed the time incorrectly from Shanks.
(Thanks to Phake Nick.)
Nauru's 1979 transition was on 02-10 at 02:00, not 05-01 at 00:00.
(Thanks to Phake Nick.)
Guam observed DST irregularly from 1959 through 1977.
(Thanks to Phake Nick.)
Hong Kong observed DST in 1941 starting 06-15 (not 04-01), then on
10-01 changed standard time to +08:30 (not +08). Its transition
back to +08 after WWII was on 1945-09-15, not the previous day.
Its 1904-10-30 change took effect at 01:00 +08 (not 00:00 LMT).
(Thanks to Phake Nick, Steve Allen, and Joseph Myers.) Also,
its 1952 fallback was on 11-02 (not 10-25).
This release contains many changes to timestamps before 1946 due
to Japanese possession or occupation of Pacific/Chuuk,
Pacific/Guam, Pacific/Kosrae, Pacific/Kwajalein, Pacific/Majuro,
Pacific/Nauru, Pacific/Palau, and Pacific/Pohnpei.
(Thanks to Phake Nick.)
Assume that the Spanish East Indies was like the Philippines and
observed American time until the end of 1844. This affects
Pacific/Chuuk, Pacific/Kosrae, Pacific/Palau, and Pacific/Pohnpei.
Changes to past tm_isdst flags
For the recent Morocco change, the tm_isdst flag should be 1 from
2018-10-27 00:00 to 2018-10-28 03:00. (Thanks to Michael Deckers.)
Give a URL to the official decree. (Thanks to Matt Johnson.)
Release 2018g - 2018-10-26 22:22:45 -0700
Briefly:
Morocco switches to permanent +01 on 2018-10-28.
Changes to future timestamps
Morocco switches from +00/+01 to permanent +01 effective 2018-10-28,
so its clocks will not fall back as previously scheduled.
(Thanks to Mohamed Essedik Najd and Brian Inglis.)
Changes to code
When generating TZif files with leap seconds, zic no longer uses a
format that trips up older 32-bit clients, fixing a bug introduced
in 2018f. (Reported by Daniel Fischer.) Also, the zic workaround
for QTBUG-53071 now also works for TZif files with leap seconds.
The translator to rearguard format now rewrites the line
"Rule Japan 1948 1951 - Sep Sat>=8 25:00 0 S" to
"Rule Japan 1948 1951 - Sep Sun>=9 1:00 0 S".
This caters to zic before 2007 and to Oracle TZUpdater 2.2.0
and earlier. (Reported by Christos Zoulas.)
Changes to past time zone abbreviations
Change HDT to HWT/HPT for WWII-era abbreviations in Hawaii.
This reverts to 2011h, as the abbreviation change in 2011i was
likely inadvertent.
Changes to documentation
tzfile.5 has new sections on interoperability issues.
Release 2018f - 2018-10-18 00:14:18 -0700
Briefly:
Volgograd moves from +03 to +04 on 2018-10-28.
Fiji ends DST 2019-01-13, not 2019-01-20.
Most of Chile changes DST dates, effective 2019-04-06.
Changes to future timestamps
Volgograd moves from +03 to +04 on 2018-10-28 at 02:00.
(Thanks to Alexander Fetisov and Stepan Golosunov.)
Fiji ends DST 2019-01-13 instead of the 2019-01-20 previously
predicted. (Thanks to Raymond Kumar.) Adjust future predictions
accordingly.
Most of Chile will end DST on the first Saturday in April at 24:00 mainland
time, and resume DST on the first Saturday in September at 24:00 mainland
time. The changes are effective from 2019-04-06, and do not affect the
Magallanes region modeled by America/Punta_Arenas. (Thanks to Juan Correa
and Tim Parenti.) Adjust future predictions accordingly.
Changes to past timestamps
The 2018-05-05 North Korea 30-minute time zone change took place
at 23:30 the previous day, not at 00:00 that day.
China's 1988 spring-forward transition was on April 17, not
April 10. Its DST transitions in 1986/91 were at 02:00, not 00:00.
(Thanks to P Chan.)
Fix several issues for Macau before 1992. Macau's pre-1904 LMT
was off by 10 s. Macau switched to +08 in 1904 not 1912, and
temporarily switched to +09/+10 during World War II. Macau
observed DST in 1942/79, not 1961/80, and there were several
errors for transition times and dates. (Thanks to P Chan.)
The 1948-1951 fallback transitions in Japan were at 25:00 on
September's second Saturday, not at 24:00. (Thanks to Phake Nick.)
zic turns this into 01:00 on the day after September's second
Saturday, which is the best that POSIX or C platforms can do.
Incorporate 1940-1949 Asia/Shanghai DST transitions from a 2014
paper by Li Yu, replacing more-questionable data from Shanks.
Changes to time zone abbreviations
Use "PST" and "PDT" for Philippine time. (Thanks to Paul Goyette.)
Changes to code
zic now always generates TZif files where time type 0 is used for
timestamps before the first transition. This simplifies the
reading of TZif files and should not affect behavior of existing
TZif readers because the same set of time types is used; only
their internal indexes may have changed. This affects only the
legacy zones EST5EDT, CST6CDT, MST7MDT, PST8PDT, CET, MET, and
EET, which previously used nonzero types for these timestamps.
Because of the type 0 change, zic no longer outputs a dummy
transition at time -2**59 (before the Big Bang), as clients should
no longer need this to handle historical timestamps correctly.
This reverts a change introduced in 2013d and shrinks most TZif
files by a few bytes.
zic now supports negative time-of-day in Rule and Leap lines, e.g.,
"Rule X min max - Apr lastSun -6:00 1:00 -" means the transition
occurs at 18:00 on the Saturday before the last Sunday in April.
This behavior was documented in 2018a but the code did not
entirely match the documentation.
localtime.c no longer requires at least one time type in TZif
files that lack transitions or have a POSIX-style TZ string. This
future-proofs the code against possible future extensions to the
format that would allow TZif files with POSIX-style TZ strings and
without transitions or time types.
A read-access subscript error in localtime.c has been fixed.
It could occur only in TZif files with timecnt == 0, something that
does not happen in practice now but could happen in future versions.
localtime.c no longer ignores TZif POSIX-style TZ strings that
specify only standard time. Instead, these TZ strings now
override the default time type for timestamps after the last
transition (or for all timestamps if there are no transitions),
just as DST strings specifying DST have always done.
leapseconds.awk now outputs "#updated" and "#expires" comments,
and supports leap seconds at the ends of months other than June
and December. (Inspired by suggestions from Chris Woodbury.)
Changes to documentation
New restrictions: A Rule name must start with a character that
is neither an ASCII digit nor "-" nor "+", and an unquoted name
should not use characters in the set "!$%&'()*,/:;<=>?@[\]^`{|}~".
The latter restriction makes room for future extensions (a
possibility noted by Tom Lane).
tzfile.5 now documents what time types apply before the first and
after the last transition, if any.
Documentation now uses the spelling "timezone" for a TZ setting
that determines timestamp history, and "time zone" for a
geographic region currently sharing the same standard time.
The name "TZif" is now used for the tz binary data format.
tz-link.htm now mentions the A0 TimeZone Migration utilities.
(Thanks to Aldrin Martoq for the link.)
Changes to build procedure
New 'make' target 'rearguard_tarballs' to build the rearguard
tarball only. This is a convenience on platforms that lack lzip
if you want to build the rearguard tarball. (Problem reported by
Deborah Goldsmith.)
tzdata.zi is now more stable from release to release. (Problem
noted by Tom Lane.) It is also a bit shorter.
tzdata.zi now can contain comment lines documenting configuration
information, such as which data format was selected, which input
files were used, and how leap seconds are treated. (Problems
noted by Lester Caine and Brian Inglis.) If the Makefile defaults
are used these comment lines are absent, for backward
compatibility. A redistributor intending to alter its copy of the
files should also append "-LABEL" to the 'version' file's first
line, where "LABEL" identifies the redistributor's change.
Release 2018e - 2018-05-01 23:42:51 -0700
Briefly:
North Korea switches back to +09 on 2018-05-05.
The main format uses negative DST again, for Ireland etc.
'make tarballs' now also builds a rearguard tarball.
New 's' and 'd' suffixes in SAVE columns of Rule and Zone lines.
Changes to past and future timestamps
North Korea switches back from +0830 to +09 on 2018-05-05.
(Thanks to Kang Seonghoon, Arthur David Olson, Seo Sanghyeon,
and Tim Parenti.)
Bring back the negative-DST changes of 2018a, except be more
compatible with data parsers that do not support negative DST.
Also, this now affects historical timestamps in Namibia and the
former Czechoslovakia, not just Ireland. The main format now uses
negative DST to model timestamps in Europe/Dublin (from 1971 on),
Europe/Prague (1946/7), and Africa/Windhoek (1994/2017). This
does not affect UT offsets, only time zone abbreviations and the
tm_isdst flag. Also, this does not affect rearguard or vanguard
formats; effectively the main format now uses vanguard instead of
rearguard format. Data parsers that do not support negative DST
can still use data from the rearguard tarball described below.
Changes to build procedure
The command 'make tarballs' now also builds the tarball
tzdataVERSION-rearguard.tar.gz, which is like tzdataVERSION.tar.gz
except that it uses rearguard format intended for trailing-edge
data parsers.
Changes to data format and to code
The SAVE column of Rule and Zone lines can now have an 's' or 'd'
suffix, which specifies whether the adjusted time is standard time
or daylight saving time. If no suffix is given, daylight saving
time is used if and only if the SAVE column is nonzero; this is
the longstanding behavior. Although this new feature is not used
in tzdata, it could be used to specify the legal time in Namibia
1994-2017, as opposed to the popular time (see below).
Changes to past timestamps
From 1994 through 2017 Namibia observed DST in winter, not summer.
That is, it used negative DST, as Ireland still does. This change
does not affect UTC offsets; it affects only the tm_isdst flag and
the abbreviation used during summer, which is now CAT, not WAST.
Although (as noted by Michael Deckers) summer and winter time were
both simply called "standard time" in Namibian law, in common
practice winter time was considered to be DST (as noted by Stephen
Colebourne). The full effect of this change is only in vanguard
and main format; in rearguard format, the tm_isdst flag is still
zero in winter and nonzero in summer.
In 1946/7 Czechoslovakia also observed negative DST in winter.
The full effect of this change is only in vanguard and main
formats; in rearguard format, it is modeled as plain GMT without
daylight saving. Also, the dates of some 1944/5 DST transitions
in Czechoslovakia have been changed.
Release 2018d - 2018-03-22 07:05:46 -0700
Briefly:
Palestine starts DST a week earlier in 2018.
Add support for vanguard and rearguard data consumers.
Add subsecond precision to source data format, though not to data.
Changes to future timestamps
In 2018, Palestine starts DST on March 24, not March 31.
Adjust future predictions accordingly. (Thanks to Sharef Mustafa.)
Changes to past and future timestamps
Casey Station in Antarctica changed from +11 to +08 on 2018-03-11
at 04:00. (Thanks to Steffen Thorsen.)
Changes to past timestamps
Historical transitions for Uruguay, represented by
America/Montevideo, have been updated per official legal documents,
replacing previous data mainly originating from the inventions of
Shanks & Pottenger. This has resulted in adjustments ranging from
30 to 90 minutes in either direction over at least two dozen
distinct periods ranging from one day to several years in length.
A mere handful of pre-1991 transitions are unaffected; data since
then has come from more reliable contemporaneous reporting. These
changes affect various timestamps in 1920-1923, 1936, 1939,
1942-1943, 1959, 1966-1970, 1972, 1974-1980, and 1988-1990.
Additionally, Uruguay's pre-standard-time UT offset has been
adjusted westward by 7 seconds, from UT-03:44:44 to UT-03:44:51, to
match the location of the Observatory of the National Meteorological
Institute in Montevideo.
(Thanks to Jeremie Bonjour, Tim Parenti, and Michael Deckers.)
Enderbury and Kiritimati skipped New Year's Eve 1994, not
New Year's Day 1995. (Thanks to Kerry Shetline.)
Fix the 1912-01-01 transition for Portugal and its colonies.
This transition was at 00:00 according to the new UT offset, not
according to the old one. Also assume that Cape Verde switched on
the same date as the rest, not in 1907. This affects
Africa/Bissau, Africa/Sao_Tome, Asia/Macau, Atlantic/Azores,
Atlantic/Cape_Verde, Atlantic/Madeira, and Europe/Lisbon.
(Thanks to Michael Deckers.)
Fix an off-by-1 error for pre-1913 timestamps in Jamaica and in
Turks & Caicos.
Changes to past time zone abbreviations
MMT took effect in Uruguay from 1908-06-10, not 1898-06-28. There
is no clock change associated with the transition.
Changes to build procedure
The new DATAFORM macro in the Makefile lets the installer choose
among three source data formats. The idea is to lessen downstream
disruption when data formats are improved.
* DATAFORM=vanguard installs from the latest, bleeding-edge
format. DATAFORM=main (the default) installs from the format
used in the 'africa' etc. files. DATAFORM=rearguard installs
from a trailing-edge format. Eventually, elements of today's
vanguard format should move to the main format, and similarly
the main format's features should eventually move to the
rearguard format.
* In the current version, the main and rearguard formats are
identical and match that of 2018c, so this change does not
affect default behavior. The vanguard format currently contains
one feature not in the main format: negative SAVE values. This
improves support for Ireland, which uses Irish Standard Time
(IST, UTC+01) in summer and GMT (UTC) in winter. tzcode has
supported negative SAVE values for decades, and this feature
should move to the main format soon. However, it will not move
to the rearguard format for quite some time because some
downstream parsers do not support it.
* The build procedure constructs three files vanguard.zi, main.zi,
and rearguard.zi, one for each format. Although the files
represent essentially the same data, they may have minor
discrepancies that users are not likely to notice. The files
are intended for downstream data consumers and are not
installed. Zoneinfo parsers that do not support negative SAVE values
should start using rearguard.zi, so that they will be unaffected
when the negative-DST feature moves from vanguard to main.
Bleeding-edge Zoneinfo parsers that support the new features
already can use vanguard.zi; in this respect, current tzcode is
bleeding-edge.
The Makefile should now be safe for parallelized builds, and 'make
-j to2050new.tzs' is now much faster on a multiprocessor host
with GNU Make.
When built with -DSUPPRESS_TZDIR, the tzcode library no longer
prepends TZDIR/ to file names that do not begin with '/'. This is
not recommended for general use, due to its security implications.
(From a suggestion by Manuela Friedrich.)
Changes to code
zic now accepts subsecond precision in expressions like
00:19:32.13, which is approximately the legal time of the
Netherlands from 1835 to 1937. However, because it is
questionable whether the few recorded uses of non-integer offsets
had subsecond precision in practice, there are no plans for tzdata
to use this feature. (Thanks to Steve Allen for pointing out
the limitations of historical data in this area.)
The code is a bit more portable to MS-Windows. Installers can
compile with -DRESERVE_STD_EXT_IDS on MS-Windows platforms that
reserve identifiers like 'localtime'. (Thanks to Manuela
Friedrich.)
Changes to documentation and commentary
theory.html now outlines tzdb's extensions to POSIX's model for
civil time, and has a section "POSIX features no longer needed"
that lists POSIX API components that are now vestigial.
(From suggestions by Steve Summit.) It also better distinguishes
time zones from tz regions. (From a suggestion by Guy Harris.)
Commentary is now more consistent about using the phrase "daylight
saving time", to match the C name tm_isdst. Daylight saving time
need not occur in summer, and need not have a positive offset from
standard time.
Commentary about historical transitions in Uruguay has been expanded
with links to many relevant legal documents.
(Thanks to Tim Parenti.)
Commentary now uses some non-ASCII characters with Unicode value
less than U+0100, as they can be useful and should work even with
older editors such as XEmacs.
Release 2018c - 2018-01-22 23:00:44 -0800
Briefly:
Revert Irish changes that relied on negative SAVE values.
Changes to tm_isdst
Revert the 2018a change to Europe/Dublin. As before, this change
does not affect UT offsets or abbreviations; it affects only
whether timestamps are considered to be standard time or
daylight-saving time, as expressed in the tm_isdst flag of C's
struct tm type. This reversion is intended to be a temporary
workaround for problems discovered with downstream uses of
releases 2018a and 2018b, which implemented Irish time by using
negative SAVE values in the Eire rules of the 'europe' file.
Although negative SAVE values have been part of tzcode for many
years and are supported by many platforms, they were not
documented before 2018a and ICU and OpenJDK do not currently
support them. A mechanism to export data to platforms lacking
support for negative DST is planned to be developed before the
change is reapplied. (Problems reported by Deborah Goldsmith and
Stephen Colebourne.)
Changes to past timestamps
Japanese DST transitions (1948-1951) were Sundays at 00:00, not
Saturdays or Sundays at 02:00. (Thanks to Takayuki Nikai.)
Changes to build procedure
The build procedure now works around mawk 1.3.3's lack of support
for character class expressions. (Problem reported by Ohyama.)
Release 2018b - 2018-01-17 23:24:48 -0800
Briefly:
Fix a packaging problem in tz2018a, which was missing 'pacificnew'.
Changes to build procedure
The distribution now contains the file 'pacificnew' again.
This file was inadvertantly omitted in the 2018a distribution.
(Problem reported by Matias Fonzo.)
Release 2018a - 2018-01-12 22:29:21 -0800
Briefly:
São Tomé and Príncipe switched from +00 to +01.
Brazil's DST will now start on November's first Sunday.
Ireland's standard time is now in the summer, not the winter.
Use Debian-style installation locations, instead of 4.3BSD-style.
New zic option -t.
Changes to past and future timestamps
São Tomé and Príncipe switched from +00 to +01 on 2018-01-01 at
01:00. (Thanks to Steffen Thorsen and Michael Deckers.)
Changes to future timestamps
Starting in 2018 southern Brazil will begin DST on November's
first Sunday instead of October's third Sunday. (Thanks to
Steffen Thorsen.)
Changes to past timestamps
A discrepancy of 4 s in timestamps before 1931 in South Sudan has
been corrected. The 'backzone' and 'zone.tab' files did not agree
with the 'africa' and 'zone1970.tab' files. (Problem reported by
Michael Deckers.)
The abbreviation invented for Bolivia Summer Time (1931-2) is now
BST instead of BOST, to be more consistent with the convention
used for Latvian Summer Time (1918-9) and for British Summer Time.
Changes to tm_isdst
Change Europe/Dublin so that it observes Irish Standard Time (UT
+01) in summer and GMT (as negative daylight-saving) in winter,
instead of observing standard time (GMT) in winter and Irish
Summer Time (UT +01) in summer. This change does not affect UT
offsets or abbreviations; it affects only whether timestamps are
considered to be standard time or daylight-saving time, as
expressed in the tm_isdst flag of C's struct tm type.
(Discrepancy noted by Derick Rethans.)
Changes to build procedure
The default installation locations have been changed to mostly
match Debian circa 2017, instead of being designed as an add-on to
4.3BSD circa 1986. This affects the Makefile macros TOPDIR,
TZDIR, MANDIR, and LIBDIR. New Makefile macros TZDEFAULT, USRDIR,
USRSHAREDIR, BINDIR, ZDUMPDIR, and ZICDIR let installers tailor
locations more precisely. (This responds to suggestions from
Brian Inglis and from Steve Summit.)
The default installation procedure no longer creates the
backward-compatibility link US/Pacific-New, which causes
confusion during user setup (e.g., see Debian bug 815200).
Use 'make BACKWARD="backward pacificnew"' to create the link
anyway, for now. Eventually we plan to remove the link entirely.
tzdata.zi now contains a version-number comment.
(Suggested by Tom Lane.)
The Makefile now quotes values like BACKWARD more carefully when
passing them to the shell. (Problem reported by Zefram.)
Builders no longer need to specify -DHAVE_SNPRINTF on platforms
that have snprintf and use pre-C99 compilers. (Problem reported
by Jon Skeet.)
Changes to code
zic has a new option -t FILE that specifies the location of the
file that determines local time when TZ is unset. The default for
this location can be configured via the new TZDEFAULT makefile
macro, which defaults to /etc/localtime.
Diagnostics and commentary now distinguish UT from UTC more
carefully; see theory.html for more information about UT vs UTC.
zic has been ported to GCC 8's -Wstringop-truncation option.
(Problem reported by Martin Sebor.)
Changes to documentation and commentary
The zic man page now documents the longstanding behavior that
times and years can be out of the usual range, with negative times
counting backwards from midnight and with year 0 preceding year 1.
(Problem reported by Michael Deckers.)
The theory.html file now mentions the POSIX limit of six chars
per abbreviation, and lists alphabetic abbreviations used.
The files tz-art.htm and tz-link.htm have been renamed to
tz-art.html and tz-link.html, respectively, for consistency with
other file names and to simplify web server configuration.
Release 2017c - 2017-10-20 14:49:34 -0700
Briefly:
Northern Cyprus switches from +03 to +02/+03 on 2017-10-29.
Fiji ends DST 2018-01-14, not 2018-01-21.
Namibia switches from +01/+02 to +02 on 2018-04-01.
Sudan switches from +03 to +02 on 2017-11-01.
Tonga likely switches from +13/+14 to +13 on 2017-11-05.
Turks & Caicos switches from -04 to -05/-04 on 2018-11-04.
A new file tzdata.zi now holds a small text copy of all data.
The zic input format has been regularized slightly.
Changes to future timestamps
Northern Cyprus has decided to resume EU rules starting
2017-10-29, thus reinstituting winter time.
Fiji ends DST 2018-01-14 instead of the 2018-01-21 previously
predicted. (Thanks to Dominic Fok.) Adjust future predictions
accordingly.
Namibia will switch from +01 with DST to +02 all year on
2017-09-03 at 02:00. This affects UT offsets starting 2018-04-01
at 02:00. (Thanks to Steffen Thorsen.)
Sudan will switch from +03 to +02 on 2017-11-01. (Thanks to Ahmed
Atyya and Yahia Abdalla.) South Sudan is not switching, so
Africa/Juba is no longer a link to Africa/Khartoum.
Tonga has likely ended its experiment with DST, and will not
adjust its clocks on 2017-11-05. Although Tonga has not announced
whether it will continue to observe DST, the IATA is assuming that
it will not. (Thanks to David Wade.)
Turks & Caicos will switch from -04 all year to -05 with US DST on
2018-03-11 at 03:00. This affects UT offsets starting 2018-11-04
at 02:00. (Thanks to Steffen Thorsen.)
Changes to past timestamps
Namibia switched from +02 to +01 on 1994-03-21, not 1994-04-03.
(Thanks to Arthur David Olson.)
Detroit did not observe DST in 1967.
Use railway time for Asia/Kolkata before 1941, by switching to
Madras local time (UT +052110) in 1870, then to IST (UT +0530) in
1906. Also, treat 1941-2's +0630 as DST, like 1942-5.
Europe/Dublin's 1946 and 1947 fallback transitions occurred at
02:00 standard time, not 02:00 DST. (Thanks to Michael Deckers.)
Pacific/Apia and Pacific/Pago_Pago switched from Antipodean to
American time in 1892, not 1879. (Thanks to Michael Deckers.)
Adjust the 1867 transition in Alaska to better reflect the
historical record, by changing it to occur on 1867-10-18 at 15:30
Sitka time rather than at the start of 1867-10-17 local time.
Although strictly speaking this is accurate only for Sitka,
the rest of Alaska's blanks need to be filled in somehow.
Fix off-by-one errors in UT offsets for Adak and Nome before 1867.
(Thanks to Michael Deckers.)
Add 7 s to the UT offset in Asia/Yangon before 1920.
Changes to zone names
Remove Canada/East-Saskatchewan from the 'backward' file, as it
exceeded the 14-character limit and was an unused misnomer anyway.
Changes to build procedure
To support applications that prefer to read time zone data in text
form, two zic input files tzdata.zi and leapseconds are now
installed by default. The commands 'zic tzdata.zi' and 'zic -L
leapseconds tzdata.zi' can reproduce the tzdata binary files
without and with leap seconds, respectively. To prevent these two
new files from being installed, use 'make TZDATA_TEXT=', and to
suppress leap seconds from the tzdata text installation, use 'make
TZDATA_TEXT=tzdata.zi'.
'make BACKWARD=' now suppresses backward-compatibility names
like 'US/Pacific' that are defined in the 'backward' and
'pacificnew' files.
'make check' now works on systems that lack a UTF-8 locale,
or that lack the nsgmls program. Set UTF8_LOCALE to configure
the name of a UTF-8 locale, if you have one.
Y2K runtime checks are no longer enabled by default. Add
-DDEPRECATE_TWO_DIGIT_YEARS to CFLAGS to enable them, instead of
adding -DNO_RUN_TIME_WARNINGS_ABOUT_YEAR_2000_PROBLEMS_THANK_YOU
to disable them. (New name suggested by Brian Inglis.)
The build procedure for zdump now works on AIX 7.1.
(Problem reported by Kees Dekker.)
Changes to code
zic and the reference runtime now reject multiple leap seconds
within 28 days of each other, or leap seconds before the Epoch.
As a result, support for double leap seconds, which was
obsolescent and undocumented, has been removed. Double leap
seconds were an error in the C89 standard; they have never existed
in civil timekeeping. (Thanks to Robert Elz and Bradley White for
noticing glitches in the code that uncovered this problem.)
zic now warns about use of the obsolescent and undocumented -y
option, and about use of the obsolescent TYPE field of Rule lines.
zic now allows unambiguous abbreviations like "Sa" and "Su" for
weekdays; formerly it rejected them due to a bug. Conversely, zic
no longer considers non-prefixes to be abbreviations; for example,
it no longer accepts "lF" as an abbreviation for "lastFriday".
Also, zic warns about the undocumented usage with a "last-"
prefix, e.g., "last-Fri".
Similarly, zic now accepts the unambiguous abbreviation "L" for
"Link" in ordinary context and for "Leap" in leap-second context.
Conversely, zic no longer accepts non-prefixes such as "La" as
abbreviations for words like "Leap".
zic no longer accepts leap second lines in ordinary input, or
ordinary lines in leap second input. Formerly, zic sometimes
warned about this undocumented usage and handled it incorrectly.
The new macro HAVE_TZNAME governs whether the tzname external
variable is exported, instead of USG_COMPAT. USG_COMPAT now
governs only the external variables "timezone" and "daylight".
This change is needed because the three variables are not in the
same category: although POSIX requires tzname, it specifies the
other two variables as optional. Also, USG_COMPAT is now 1 or 0:
if not defined, the code attempts to guess it from other macros.
localtime.c and difftime.c no longer require stdio.h, and .c files
other than zic.c no longer require sys/wait.h.
zdump.c no longer assumes snprintf. (Reported by Jonathan Leffler.)
Calculation of time_t extrema works around a bug in GCC 4.8.4
(Reported by Stan Shebs and Joseph Myers.)
zic.c no longer mistranslates formats of line numbers in non-English
locales. (Problem reported by Benno Schulenberg.)
Several minor changes have been made to the code to make it a
bit easier to port to MS-Windows and Solaris. (Thanks to Kees
Dekker for reporting the problems.)
Changes to documentation and commentary
The two new files 'theory.html' and 'calendars' contain the
contents of the removed file 'Theory'. The goal is to document
tzdb theory more accessibly.
The zic man page now documents abbreviation rules.
tz-link.htm now covers how to apply tzdata changes to clients.
(Thanks to Jorge Fábregas for the AIX link.) It also mentions MySQL.
The leap-seconds.list URL has been updated to something that is
more reliable for tzdb. (Thanks to Tim Parenti and Brian Inglis.)
Release 2017b - 2017-03-17 07:30:38 -0700
Briefly: Haiti has resumed DST.
Changes to past and future timestamps
Haiti resumed observance of DST in 2017. (Thanks to Steffen Thorsen.)
Changes to past timestamps
Liberia changed from -004430 to +00 on 1972-01-07, not 1972-05-01.
Use "MMT" to abbreviate Liberia's time zone before 1972, as "-004430"
is one byte over the POSIX limit. (Problem reported by Derick Rethans.)
Changes to code
The reference localtime implementation now falls back on the