diff options
| -rw-r--r-- | Makefile | 29 | ||||
| -rw-r--r-- | NEWS | 53 | ||||
| -rw-r--r-- | README | 4 | ||||
| -rw-r--r-- | africa | 10 | ||||
| -rw-r--r-- | asia | 42 | ||||
| -rw-r--r-- | backward | 3 | ||||
| -rw-r--r-- | backzone | 4 | ||||
| -rw-r--r-- | etcetera | 1 | ||||
| -rw-r--r-- | europe | 4 | ||||
| -rw-r--r-- | iso3166.tab | 8 | ||||
| -rw-r--r-- | leap-seconds.list | 8 | ||||
| -rw-r--r-- | leapseconds | 6 | ||||
| -rw-r--r-- | northamerica | 11 | ||||
| -rw-r--r-- | theory.html | 91 | ||||
| -rw-r--r-- | version | 2 |
15 files changed, 207 insertions, 69 deletions
@@ -12,7 +12,10 @@ VERSION= unknown # Email address for bug reports. BUGEMAIL= tz@iana.org -# Choose source data features. To get new features right away, use: +# DATAFORM selects the data format. +# Available formats represent essentially the same data, albeit +# possibly with minor discrepancies that users are not likely to notice. +# To get new features and the best data right away, use: # DATAFORM= vanguard # To wait a while before using new features, to give downstream users # time to upgrade zic (the default), use: @@ -33,11 +36,11 @@ DATAFORM= main LOCALTIME= GMT # If you want something other than Eastern United States time as a template -# for handling POSIX-style timezone environment variables, +# for handling ruleless POSIX-style timezone environment variables, # change the line below (after finding the timezone you want in the # one of the $(TDATA) source files, or adding it to a source file). -# When a POSIX-style environment variable is handled, the rules in the -# template file are used to determine "spring forward" and "fall back" days and +# A ruleless environment setting like TZ='CST6CDT' uses the rules in the +# template file to determine "spring forward" and "fall back" days and # times; the environment variable itself specifies UT offsets of standard and # daylight saving time. # Alternatively, if you discover you've got the wrong timezone, you can just @@ -46,7 +49,6 @@ LOCALTIME= GMT # Use the command # make zonenames # to get a list of the values you can use for POSIXRULES. -# If you want POSIX compatibility, use "America/New_York". POSIXRULES= America/New_York @@ -113,8 +115,8 @@ TIME_T_ALTERNATIVES = $(TIME_T_ALTERNATIVES_HEAD) $(TIME_T_ALTERNATIVES_TAIL) TIME_T_ALTERNATIVES_HEAD = int64_t TIME_T_ALTERNATIVES_TAIL = int32_t uint32_t uint64_t -# What kind of TZif data files to generate. -# (TZif is the binary time zone data format that zic generates.) +# What kind of TZif data files to generate. (TZif is the binary time +# zone data format that zic generates; see Internet RFC 8536.) # If you want only POSIX time, with time values interpreted as # seconds since the epoch (not counting leap seconds), use # REDO= posix_only @@ -360,6 +362,9 @@ LEAPSECONDS= zic= ./zic ZIC= $(zic) $(ZFLAGS) +# To shrink the size of installed TZif files, +# append "-r @N" to omit data before N-seconds-after-the-Epoch. +# See the zic man page for more about -r. ZFLAGS= # How to use zic to install TZif files. @@ -491,7 +496,8 @@ MANTXTS= newctime.3.txt newstrftime.3.txt newtzset.3.txt \ COMMON= calendars CONTRIBUTING LICENSE Makefile \ NEWS README theory.html version WEB_PAGES= tz-art.html tz-how-to.html tz-link.html -CHECK_WEB_PAGES=check_tz-art.html check_tz-how-to.html check_tz-link.html +CHECK_WEB_PAGES=check_theory.html check_tz-art.html \ + check_tz-how-to.html check_tz-link.html DOCS= $(MANS) date.1 $(MANTXTS) $(WEB_PAGES) PRIMARY_YDATA= africa antarctica asia australasia \ europe northamerica southamerica @@ -804,9 +810,10 @@ check_tzs: $(TZS) $(TZS_NEW) touch $@ check_web: $(CHECK_WEB_PAGES) +check_theory.html: theory.html check_tz-art.html: tz-art.html check_tz-link.html: tz-link.html -check_tz-art.html check_tz-link.html: +check_theory.html check_tz-art.html check_tz-link.html: $(CURL) -sS --url https://validator.w3.org/nu/ -F out=gnu \ -F file=@$$(expr $@ : 'check_\(.*\)') -o $@.out && \ test ! -s $@.out || { cat $@.out; exit 1; } @@ -840,11 +847,13 @@ check_zishrink_posix check_zishrink_right: \ touch $@ clean_misc: + rm -fr check_*.dir rm -f *.o *.out $(TIME_T_ALTERNATIVES) \ check_* core typecheck_* \ date tzselect version.h zdump zic yearistype libtz.a clean: clean_misc - rm -fr *.dir *.zi tzdb-*/ $(TZS_NEW) + rm -fr *.dir tzdb-*/ + rm -f *.zi $(TZS_NEW) maintainer-clean: clean @echo 'This command is intended for maintainers to use; it' @@ -1,5 +1,53 @@ News for the tz database +Release 20198 - 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: @@ -400,8 +448,9 @@ Release 2018d - 2018-03-22 07:05:46 -0700 downstream parsers do not support it. * The build procedure constructs three files vanguard.zi, main.zi, - and rearguard.zi, one for each format. The files represent the - same data as closely as the formats allow. These three files + 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 @@ -1,7 +1,7 @@ README for the tz distribution -"What time is it?" -- Richard Deacon as The King -"Any time you want it to be." -- Frank Baxter as The Scientist +"Where do I set the hands of the clock?" -- Les Tremayne as The King +"Oh that--you can set them any place you want." -- Frank Baxter as The Scientist (from the Bell System film "About Time") The Time Zone Database (called tz, tzdb or zoneinfo) contains code and @@ -364,6 +364,11 @@ Zone Africa/Cairo 2:05:09 - LMT 1900 Oct # See Africa/Lagos. # Eritrea +# See Africa/Nairobi. + +# Eswatini (formerly Swaziland) +# See Africa/Johannesburg. + # Ethiopia # See Africa/Nairobi. # @@ -1188,7 +1193,7 @@ Zone Africa/Johannesburg 1:52:00 - LMT 1892 Feb 8 1:30 - SAST 1903 Mar 2:00 SA SAST Link Africa/Johannesburg Africa/Maseru # Lesotho -Link Africa/Johannesburg Africa/Mbabane # Swaziland +Link Africa/Johannesburg Africa/Mbabane # Eswatini # # Marion and Prince Edward Is # scientific station since 1947 @@ -1230,9 +1235,6 @@ Zone Africa/Juba 2:06:28 - LMT 1931 2:00 Sudan CA%sT 2000 Jan 15 12:00 3:00 - EAT -# Swaziland -# See Africa/Johannesburg. - # Tanzania # See Africa/Nairobi. @@ -1620,6 +1620,24 @@ Rule Zion 1974 only - Jul 7 0:00 1:00 D Rule Zion 1974 only - Oct 13 0:00 0 S Rule Zion 1975 only - Apr 20 0:00 1:00 D Rule Zion 1975 only - Aug 31 0:00 0 S + +# From Alois Treindl (2019-03-06): +# http://www.moin.gov.il/Documents/שעון קיץ/clock-50-years-7-2014.pdf +# From Isaac Starkman (2019-03-06): +# Summer time was in that period in 1980 and 1984, see +# https://www.ynet.co.il/articles/0,7340,L-3951073,00.html +# You can of course read it in translation. +# I checked the local newspapers for that years. +# It started on midnight and end at 01.00 am. +# From Paul Eggert (2019-03-06): +# Also see this thread about the moin.gov.il URL: +# https://mm.icann.org/pipermail/tz/2018-November/027194.html +Rule Zion 1980 only - Aug 2 0:00 1:00 D +Rule Zion 1980 only - Sep 13 1:00 0 S +Rule Zion 1984 only - May 5 0:00 1:00 D +Rule Zion 1984 only - Aug 25 1:00 0 S + +# From Shanks & Pottenger: Rule Zion 1985 only - Apr 14 0:00 1:00 D Rule Zion 1985 only - Sep 15 0:00 0 S Rule Zion 1986 only - May 18 0:00 1:00 D @@ -3071,9 +3089,15 @@ Zone Asia/Karachi 4:28:12 - LMT 1907 # the official website, though the decree did not specify the exact # time of the time shift. # http://www.palestinecabinet.gov.ps/Website/AR/NDecrees/ViewFile.ashx?ID=e7a42ab7-ee23-435a-b9c8-a4f7e81f3817 + +# From Even Scharning (2019-03-23): +# DST in Palestine will start on 30 March this year, not 23 March as the time +# zone database predicted. +# https://ramallah.news/post/123610 # -# From Paul Eggert (2018-03-16): -# For 2016 on, predict spring transitions on March's fourth Saturday at 01:00. +# From Tim Parenti (2019-03-23): +# Combining this with the rules observed since 2016, adjust our spring +# transition guess to Mar Sat>=24. # Rule NAME FROM TO TYPE IN ON AT SAVE LETTER/S Rule EgyptAsia 1957 only - May 10 0:00 1:00 S @@ -3104,7 +3128,7 @@ Rule Palestine 2012 only - Sep 21 1:00 0 - Rule Palestine 2013 only - Sep Fri>=21 0:00 0 - Rule Palestine 2014 2015 - Oct Fri>=21 0:00 0 - Rule Palestine 2015 only - Mar lastFri 24:00 1:00 S -Rule Palestine 2016 max - Mar Sat>=22 1:00 1:00 S +Rule Palestine 2016 max - Mar Sat>=24 1:00 1:00 S Rule Palestine 2016 max - Oct lastSat 1:00 0 - # Zone NAME GMTOFF RULES FORMAT [UNTIL] @@ -3596,5 +3620,17 @@ Zone Asia/Ho_Chi_Minh 7:06:40 - LMT 1906 Jul 1 8:00 - +08 1975 Jun 13 7:00 - +07 +# From Paul Eggert (2019-02-19): +# +# The Ho Chi Minh entry suffices for most purposes as it agrees with all of +# Vietnam since 1975-06-13. Presumably clocks often changed in south Vietnam +# in the early 1970s as locations changed hands during the war; however the +# details are unknown and would likely be too voluminous for this database. +# +# For timestamps in north Vietnam back to 1970 (the tzdb cutoff), +# use Asia/Bangkok; see the VN entries in the file zone1970.tab. +# For timestamps before 1970, see Asia/Hanoi in the file 'backzone'. + + # Yemen # See Asia/Riyadh. @@ -77,6 +77,7 @@ Link Pacific/Easter Chile/EasterIsland Link America/Havana Cuba Link Africa/Cairo Egypt Link Europe/Dublin Eire +Link Etc/UTC Etc/UCT Link Europe/London Europe/Belfast Link Europe/Chisinau Europe/Tiraspol Link Europe/London GB @@ -111,7 +112,7 @@ Link Asia/Taipei ROC Link Asia/Seoul ROK Link Asia/Singapore Singapore Link Europe/Istanbul Turkey -Link Etc/UCT UCT +Link Etc/UTC UCT Link America/Anchorage US/Alaska Link America/Adak US/Aleutian Link America/Phoenix US/Arizona @@ -204,7 +204,7 @@ Zone Africa/Maseru 1:50:00 - LMT 1903 Mar 2:00 1:00 SAST 1944 Mar 19 2:00 2:00 - SAST -# Swaziland +# Eswatini (formerly Swaziland) Zone Africa/Mbabane 2:04:24 - LMT 1903 Mar 2:00 - SAST @@ -625,7 +625,7 @@ Zone Europe/Sarajevo 1:13:40 - LMT 1884 1:00 - CET 1982 Nov 27 1:00 EU CE%sT -# Macedonia +# North Macedonia Zone Europe/Skopje 1:25:44 - LMT 1884 1:00 - CET 1941 Apr 18 23:00 1:00 C-Eur CE%sT 1945 May 8 2:00s @@ -19,7 +19,6 @@ Zone Etc/GMT 0 - GMT Zone Etc/UTC 0 - UTC -Zone Etc/UCT 0 - UCT # The following link uses older naming conventions, # but it belongs here, not in the file 'backward', @@ -1855,7 +1855,7 @@ Zone Europe/Luxembourg 0:24:36 - LMT 1904 Jun 1:00 Belgium CE%sT 1977 1:00 EU CE%sT -# Macedonia +# North Macedonia # See Europe/Belgrade. # Malta @@ -3359,7 +3359,7 @@ Zone Europe/Belgrade 1:22:00 - LMT 1884 Link Europe/Belgrade Europe/Ljubljana # Slovenia Link Europe/Belgrade Europe/Podgorica # Montenegro Link Europe/Belgrade Europe/Sarajevo # Bosnia and Herzegovina -Link Europe/Belgrade Europe/Skopje # Macedonia +Link Europe/Belgrade Europe/Skopje # North Macedonia Link Europe/Belgrade Europe/Zagreb # Croatia # Slovakia diff --git a/iso3166.tab b/iso3166.tab index c2e0f8eafc01..a4ff61a4d321 100644 --- a/iso3166.tab +++ b/iso3166.tab @@ -9,8 +9,8 @@ # All text uses UTF-8 encoding. The columns of the table are as follows: # # 1. ISO 3166-1 alpha-2 country code, current as of -# ISO 3166-1 N905 (2016-11-15). See: Updates on ISO 3166-1 -# http://isotc.iso.org/livelink/livelink/Open/16944257 +# ISO 3166-1 N976 (2018-11-06). See: Updates on ISO 3166-1 +# https://isotc.iso.org/livelink/livelink/Open/16944257 # 2. The usual English name for the coded region, # chosen so that alphabetic sorting of subsets produces helpful lists. # This is not the same as the English name in the ISO 3166 tables. @@ -166,7 +166,7 @@ ME Montenegro MF St Martin (French) MG Madagascar MH Marshall Islands -MK Macedonia +MK North Macedonia ML Mali MM Myanmar (Burma) MN Mongolia @@ -235,7 +235,7 @@ ST Sao Tome & Principe SV El Salvador SX St Maarten (Dutch) SY Syria -SZ Swaziland +SZ Eswatini (Swaziland) TC Turks & Caicos Is TD Chad TF French Southern & Antarctic Lands diff --git a/leap-seconds.list b/leap-seconds.list index cf54b9aa3eb2..fd3d192ea9ff 100644 --- a/leap-seconds.list +++ b/leap-seconds.list @@ -204,10 +204,10 @@ # current -- the update time stamp, the data and the name of the file # will not change. # -# Updated through IERS Bulletin C56 -# File expires on: 28 June 2019 +# Updated through IERS Bulletin C57 +# File expires on: 28 December 2019 # -#@ 3770668800 +#@ 3786480000 # 2272060800 10 # 1 Jan 1972 2287785600 11 # 1 Jul 1972 @@ -252,4 +252,4 @@ # the hash line is also ignored in the # computation. # -#h 62ca19f6 96a4ae0a 3708451c 9f8693f4 016604eb +#h 83c68138 d3650221 07dbbbcd 11fcc859 ced1106a diff --git a/leapseconds b/leapseconds index 325f3a1d1383..886ae273e159 100644 --- a/leapseconds +++ b/leapseconds @@ -63,7 +63,7 @@ Leap 2016 Dec 31 23:59:60 + S # POSIX timestamps for the data in this file: #updated 1467936000 -#expires 1561680000 +#expires 1577491200 -# Updated through IERS Bulletin C56 -# File expires on: 28 June 2019 +# Updated through IERS Bulletin C57 +# File expires on: 28 December 2019 diff --git a/northamerica b/northamerica index faaf97920efe..eee8de0fbc7a 100644 --- a/northamerica +++ b/northamerica @@ -609,6 +609,15 @@ Zone America/Los_Angeles -7:52:58 - LMT 1883 Nov 18 12:07:02 # In a 2018-12-11 special election, Metlakatla voted to go back to # Alaska time (including daylight saving time) starting next year. # https://www.krbd.org/2018/12/12/metlakatla-to-follow-alaska-standard-time-allow-liquor-sales/ +# +# From Ryan Stanley (2019-01-11): +# The community will be changing back on the 20th of this month... +# From Tim Parenti (2019-01-11): +# Per an announcement on the Metlakatla community's official Facebook page, the +# "fall back" will be on Sunday 2019-01-20 at 02:00: +# https://www.facebook.com/141055983004923/photos/607150969728753/ +# So they won't be waiting for Alaska to join them on 2019-03-10, but will +# rather change their clocks twice in seven weeks. # Zone NAME GMTOFF RULES FORMAT [UNTIL] Zone America/Juneau 15:02:19 - LMT 1867 Oct 19 15:33:32 @@ -637,7 +646,7 @@ Zone America/Metlakatla 15:13:42 - LMT 1867 Oct 19 15:44:55 -8:00 US P%sT 1983 Oct 30 2:00 -8:00 - PST 2015 Nov 1 2:00 -9:00 US AK%sT 2018 Nov 4 2:00 - -8:00 - PST 2019 Mar Sun>=8 3:00 + -8:00 - PST 2019 Jan 20 2:00 -9:00 US AK%sT Zone America/Yakutat 14:41:05 - LMT 1867 Oct 19 15:12:18 -9:18:55 - LMT 1900 Aug 20 12:00 diff --git a/theory.html b/theory.html index a8da06547603..e37302234daf 100644 --- a/theory.html +++ b/theory.html @@ -15,7 +15,7 @@ <ul> <li><a href="#scope">Scope of the <code><abbr>tz</abbr></code> database</a></li> - <li><a href="#naming">Names of timezones</a></li> + <li><a href="#naming">Timezone identifiers</a></li> <li><a href="#abbreviations">Time zone abbreviations</a></li> <li><a href="#accuracy">Accuracy of the <code><abbr>tz</abbr></code> database</a></li> @@ -107,9 +107,9 @@ It does not always make sense to talk about a timezone's </section> <section> - <h2 id="naming">Names of timezones</h2> + <h2 id="naming">Timezone identifiers</h2> <p> -Each timezone has a unique name. +Each timezone has a name that uniquely identifies the timezone. Inexperienced users are not expected to select these names unaided. Distributors should provide documentation and/or a simple selection interface that explains each name via a map or via descriptive text like @@ -142,10 +142,12 @@ among the following goals: </li> <li> Be robust in the presence of political changes. - For example, names of countries are ordinarily not used, to avoid + For example, names are typically not tied to countries, to avoid incompatibilities when countries change their name (e.g., - Zaire→Congo) or when locations change countries (e.g., Hong + Swaziland→Eswatini) or when locations change countries (e.g., Hong Kong from UK colony to China). + There is no requirement that every country or national + capital must have a timezone name. </li> <li> Be portable to a wide variety of implementations. @@ -215,19 +217,18 @@ in decreasing order of importance: do not need locations, since local time is not defined there. </li> <li> - There should typically be at least one name for each <a - href="https://en.wikipedia.org/wiki/ISO_3166-1"><abbr - title="International Organization for Standardization">ISO</abbr> - 3166-1</a> officially assigned two-letter code for an inhabited - country or territory. - </li> - <li> If all the clocks in a timezone have agreed since 1970, do not bother to include more than one timezone even if some of the clocks disagreed before 1970. Otherwise these tables would become annoyingly large. </li> <li> + If boundaries between regions are fluid, such as during a war or + insurrection, do not bother to create a new timezone merely + because of yet another boundary change. This helps prevent table + bloat and simplifies maintenance. + </li> + <li> If a name is ambiguous, use a less ambiguous alternative; e.g., many cities are named San José and Georgetown, so prefer <code>America/Costa_Rica</code> to @@ -299,29 +300,23 @@ in decreasing order of importance: </ul> <p> -The file '<code>zone1970.tab</code>' lists geographical locations used -to name timezones. -It is intended to be an exhaustive list of names for geographic -regions as described above; this is a subset of the timezones in the data. -Although a '<code>zone1970.tab</code>' location's -<a href="https://en.wikipedia.org/wiki/Longitude">longitude</a> -corresponds to -its <a href="https://en.wikipedia.org/wiki/Local_mean_time">local mean -time (<abbr>LMT</abbr>)</a> offset with one hour for every 15° -east longitude, this relationship is not exact. +Guidelines have evolved with time, and names following old versions of +this guideline might not follow the current version. When guidelines +have changed, old names continue to be supported. Guideline changes +have included the following: </p> -<p> -Older versions of this package used a different naming scheme, -and these older names are still supported. +<ul> +<li> +Older versions of this package used a different naming scheme. See the file '<code>backward</code>' for most of these older names (e.g., '<code>US/Eastern</code>' instead of '<code>America/New_York</code>'). The other old-fashioned names still supported are '<code>WET</code>', '<code>CET</code>', '<code>MET</code>', and '<code>EET</code>' (see the file '<code>europe</code>'). -</p> +</li> -<p> +<li> Older versions of this package defined legacy names that are incompatible with the first guideline of location names, but which are still supported. @@ -332,6 +327,31 @@ Also, the file '<code>backward</code>' defines the legacy names and the file '<code>northamerica</code>' defines the legacy names '<code>EST5EDT</code>', '<code>CST6CDT</code>', '<code>MST7MDT</code>', and '<code>PST8PDT</code>'. +</li> + +<li> +Older versions of this guideline said that +there should typically be at least one name for each <a +href="https://en.wikipedia.org/wiki/ISO_3166-1"><abbr +title="International Organization for Standardization">ISO</abbr> +3166-1</a> officially assigned two-letter code for an inhabited +country or territory. +This old guideline has been dropped, as it was not needed to handle +timestamps correctly and it increased maintenance burden. +</li> +</ul> + +<p> +The file '<code>zone1970.tab</code>' lists geographical locations used +to name timezones. +It is intended to be an exhaustive list of names for geographic +regions as described above; this is a subset of the timezones in the data. +Although a '<code>zone1970.tab</code>' location's +<a href="https://en.wikipedia.org/wiki/Longitude">longitude</a> +corresponds to +its <a href="https://en.wikipedia.org/wiki/Local_mean_time">local mean +time (<abbr>LMT</abbr>)</a> offset with one hour for every 15° +east longitude, this relationship is not exact. </p> <p> @@ -983,7 +1003,9 @@ an older <code>zic</code>. constrained to be a string containing abbreviations and numeric data as described <a href="#POSIX">above</a>. The file's format is <dfn><abbr>TZif</abbr></dfn>, - a timezone information format that contains binary data. + a timezone information format that contains binary data; see + <a href="https://tools.ietf.org/html/8536">Internet + <abbr>RFC</abbr> 8536</a>. The daylight saving time rules to be used for a particular timezone are encoded in the <abbr>TZif</abbr> file; the format of the file allows <abbr>US</abbr>, @@ -1166,7 +1188,7 @@ The <code><abbr>tz</abbr></code> code and data supply the following interfaces: <ul> <li> A set of timezone names as per - "<a href="#naming">Names of timezones</a>" above. + "<a href="#naming">Timezone identifiers</a>" above. </li> <li> Library functions described in "<a href="#functions">Time and date @@ -1213,6 +1235,17 @@ For example, users should not rely on particular <abbr>UT</abbr> offsets or abbreviations for timestamps, as data entries are often based on guesswork and these guesses may be corrected or improved. </p> + +<p> +Timezone boundaries are not part of the stable interface. +For example, even though the <samp>Asia/Bangkok</samp> timezone +currently includes Chang Mai, Hanoi, and Phnom Penh, this is not part +of the stable interface and the timezone can split at any time. +If a calendar application records a future event in some location other +than Bangkok by putting "<samp>Asia/Bangkok</samp>" in the event's record, +the application should be robust in the presence of timezone splits +between now and the future time. +</p> </section> <section> @@ -1 +1 @@ -2018i +2019a |