[Mon Oct 23 16:02:09 UTC 2017]

The 2017c release of the tz code and data is available. It reflects the
following changes, which were either circulated on the tz mailing list or are
relatively minor technical or administrative changes:

   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 time stamps

     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 time stamps

     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.)

Here are links to the release files:

   https://www.iana.org/time-zones/repository/releases/tzcode2017c.tar.gz
   https://www.iana.org/time-zones/repository/releases/tzdata2017c.tar.gz
   https://www.iana.org/time-zones/repository/releases/tzdb-2017c.tar.lz

Links are also available via plain HTTP, and via FTP from
ftp://ftp.iana.org/tz/releases with the same basenames as above.