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Diffstat (limited to 'tz/NEWS')
| -rw-r--r-- | tz/NEWS | 229 |
1 files changed, 226 insertions, 3 deletions
@@ -1,5 +1,228 @@ News for the tz database +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-compatility 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 @@ -31,7 +254,7 @@ Release 2020e - 2020-12-22 15:14:34 -0800 Correct many pre-1986 transitions, fixing entries originally derived from Shanks. The fixes include: - Australia: several 1917 through 1971 transitions - - Bahamas: several 1941 through 1945 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 @@ -825,8 +1048,8 @@ Release 2018d - 2018-03-22 07:05:46 -0700 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.) + 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 |