Time Zone Database Release 2018d
Released
Downloads
| File | Description |
|---|---|
 tzdb-2018d.tar.lz (424.8kb) |
Complete Distribution (Data, Code and Extras) |
| tzdata2018d.tar.gz (343.0kb) |
Data Only Distribution |
| tzcode2018d.tar.gz (224.5kb) |
Code Only Distribution |
Release Notes
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.)
East Kiribati 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.