Lines Matching +full:pre +full:- +full:clocks
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34 href="https://www.iana.org/time-zones"><code><abbr>tz</abbr></code>
37 It organizes <a href="tz-link.html">time zone and daylight saving time
40 whose clocks all agree about timestamps that occur after the <a
42 (1970-01-01 00:00:00 <a
45 Although 1970 is a somewhat-arbitrary cutoff, there are significant
56 smaller than a traditional time zone, because clocks in a timezone
61 <code>America/Denver</code> which observes US-style daylight saving
72 Clock transitions before 1970 are recorded for location-based timezones,
74 misbehave if data entries were omitted for pre-1970 transitions.
78 details of pre-1970 civil timekeeping.
91 href="https://en.wikipedia.org/wiki/Unix">UNIX</a>-like systems.
92 As of this writing, the current edition of POSIX is POSIX.1-2024,
94 Unlike its predecessor POSIX.1-2017 (<a
96 Group Base Specifications Issue 7</a>, IEEE Std 1003.1-2017, 2018
97 Edition), POSIX.1-2024 requires support for the
100 standard and daylight saving times required by POSIX.1-2017.
129 locale-dependent strings like "Prague", "Praha", "Прага", and "布拉格".
139 Uniquely identify every timezone where clocks have agreed since 1970.
140 This is essential for the intended use: static clocks keeping local
144 Indicate to experts where the timezone's clocks typically are.
190 '<code>.</code>', '<code>-</code>' and '<code>_</code>'.
195 '<code>-</code>'.
206 Although the reference implementation is case-sensitive, some
223 If all the clocks in a timezone have agreed since 1970,
225 even if some of the clocks disagreed before 1970.
263 Among locations with similar populations, pick the best-known
303 a location's consensus English-language spelling changes; for example,
305 due to long-time widespread use of the new city name instead of the old.
321 The other old-fashioned names still supported are
333 '<code>Etc/GMT0</code>', '<code>Etc/GMT-0</code>', '<code>Etc/GMT+0</code>',
334 '<code>GMT0</code>', '<code>GMT-0</code>' and '<code>GMT+0</code>',
343 href="https://en.wikipedia.org/wiki/ISO_3166-1"><abbr
345 3166-1</a> officially assigned two-letter code for an inhabited
363 The backward-compatibility file <code>zone.tab</code> is similar
364 but conforms to the older-version guidelines related to <abbr>ISO</abbr> 3166-1;
369 into regions where clocks agree now and in the predicted future;
384 like <code><+08>-8</code>;
407 '<code>+</code>' or '<code>-</code>'.
416 Previous editions of this guideline required upper-case letters, but the
419 Standard Time</a> preferred "ChST", so lower-case letters are now
421 Also, POSIX from 2001 on relaxed the rule to allow '<code>-</code>',
425 '<code>-</code>' are safe in all locales.
429 expression <code>[-+[:alnum:]]{3,6}</code> should match the
436 Use abbreviations that are in common use among English-speakers,
447 AHST/AHDT Alaska-Hawaii,
468 MET/MEST Middle European (a backward-compatibility alias for
497 Typically, numeric abbreviations (e.g., '<code>-</code>004430' for
510 FFMT Fort-de-France;
523 PPMT Port-au-Prince;
555 <code>-</code>05 and <code>+</code>0530 that are generated
564 English, and the database uses 'CET' even for circa-1910
578 (<abbr>UT</abbr>) (with time zone abbreviation '<code>-</code>00') for
580 The leading '<code>-</code>' is a flag that the <abbr>UT</abbr> offset is in
598 '<code>-</code>0600' instead of time zone abbreviations like 'CST'.
627 The pre-1970 entries in this database cover only a tiny sliver of how
628 clocks actually behaved; the vast majority of the necessary
647 href="https://www.dissentmagazine.org/blog/booked-a-global-history-of-time-vanessa-ogle">Booked:
648 A Global History of Time</a>. <cite>Dissent</cite> 2015-12-17.
651 Most of the pre-1970 data entries come from unreliable sources, often
661 years of first-class work done by
663 "<a href="https://www.polyomino.org.uk/british-time/">History of
668 Sometimes, different people in the same city maintain clocks
672 agree with each other), church-clock time was used for birth
685 database stands for the containing region, its pre-1970 data
688 Kingdom, but its pre-1847 times are valid only for locations that
699 but the date of standardization (1880-08-02) is not in the
722 Early timekeeping practices, even assuming perfect clocks, were
727 The <code><abbr>tz</abbr></code> database cannot represent stopped clocks.
728 However, on 1911-03-11 at 00:00, some public-facing French clocks
737 For example, from 1880 to 1916 clocks in Ireland observed Dublin Mean
749 For example, from 1922 until World War II the UK moved clocks
751 was Easter, in which case it moved clocks forward the previous
767 Gregorian calendar</a> with days containing 24 equal-length hours
769 Pre-standard time is modeled as local mean time.
775 timekeeping</a> had twelve varying-length daytime hours with a
776 non-hour-based system at night.
778 calendar with 24-hour days. These divergences range from
780 wee hours of the morning, to more-significant differences such as <a
781 href="https://theworld.org/stories/2015-01-30/if-you-have-meeting-ethiopia-you-better-double-check-time">the
789 like <code><-03>3</code> or <code>America/Cayenne</code> starts
793 Early clocks were less reliable, and data entries do not represent
810 and since pre-1972 <abbr>UTC</abbr> seconds varied in length,
822 to more than about one-hour accuracy.
839 practice POSIX clocks more typically either progress glacially during
854 database's pre-1970 and future timestamps are either wrong or
874 <a href="tz-link.html#tzdb">part of many platforms</a>, where the
875 primary use of this package is to update obsolete time-related files.
890 like <code>CET-1CEST,M3.5.0,M10.5.0/3</code> uses a complex
904 <h3 id="POSIX.1-2017">POSIX.1-2017 properties and limitations</h3>
906 Some platforms support only the features required by POSIX.1-2017,
907 and have not yet upgraded to POSIX.1-2024.
914 POSIX.1-2017 does not require support for geographical <code>TZ</code>,
923 which is all that POSIX.1-2017 requires,
924 has a format that is hard to describe and is error-prone in practice.
947 Starting with POSIX.1-2001, <var>std</var> and <var>dst</var>
949 this allows "<code>+</code>" and "<code>-</code>" in the names.
971 leading '<code>+</code>' or '<code>-</code>' is not allowed.
977 origin-1 day number not counting February 29
980 origin-0 day number counting February 29 if present
1007 <pre><code>TZ='NZST-12NZDT,M9.5.0,M4.1.0/3'</code></pre>
1015 <pre><code>TZ='Pacific/Auckland'</code></pre>
1020 POSIX.1-2017 also has the limitations of POSIX.1-2024,
1024 <h3 id="POSIX.1-2024">POSIX.1-2024 properties and limitations</h3>
1026 POSIX.1-2024 extends POSIX.1-2017 in the following significant ways:
1030 POSIX.1-2024 requires support for geographical <code>TZ</code>.
1034 POSIX.1-2024 requires <code>struct tm</code>
1043 like <code>"<-02>2<-01>,M3.5.0/-1,M10.5.0/0"</code>
1048 However POSIX.1-2024, like earlier POSIX editions, has some limitations:
1051 The <code>TZ</code> environment variable is process-global, which
1052 makes it hard to write efficient, thread-safe applications that
1056 In POSIX, there is no tamper-proof way for a process to learn the
1065 limit phone calls to off-peak hours.
1086 <h3 id="POSIX-extensions">Extensions to POSIX in the
1099 since 1970-01-01 00:00:00 <abbr>UTC</abbr>, ignoring leap seconds.
1100 In practice, <code>time_t</code> is usually a signed 64- or 32-bit
1101 integer; 32-bit signed <code>time_t</code> values stop working after
1102 2038-01-19 03:14:07 <abbr>UTC</abbr>, so new implementations these
1103 days typically use a signed 64-bit integer.
1104 Unsigned 32-bit integers are used on one or two platforms, and 36-bit
1105 and 40-bit integers are also used occasionally.
1107 floating-point type, this was not supported by any practical system,
1108 and POSIX.1-2013+ and the <code><abbr>tz</abbr></code> code both
1115 the name of a file from which time-related information is read.
1142 assume pre-POSIX <code>TZ</code> values.
1148 more-efficient thread-safe applications that need to use multiple
1172 they are not needed, and are relics of a too-simple model that does
1173 not suffice to handle many real-world timestamps.
1214 <h3 id="other-portability">Other portability notes</h3>
1224 may now examine <code>localtime(&clock)->tm_zone</code>
1226 <code>tzname[localtime(&clock)->tm_isdst]</code>
1240 In <abbr>SVR2</abbr>, time conversion fails for near-minimum or
1241 near-maximum <code>time_t</code> values when doing conversions
1318 <a href="tz-link.html#download">Downloading
1349 <a href="https://www.bipm.org/en/cgpm-2022/resolution-4">plans
1364 <a href="tz-link.html#precision">Precision timekeeping</a>,
1369 However, kernel-clock twiddling approximates UTC only roughly,
1386 calls to <code>gmtime</code>-like functions
1402 If the POSIX-compatible <abbr>TZif</abbr> file set is installed
1404 leap-second-aware file set is by default installed in a separate
1405 directory <samp>zoneinfo-leaps</samp>.
1408 processes being leap-second aware while other processes are
1409 POSIX-compatible; the leap-second choice is system-wide.
1411 discard <samp>zoneinfo</samp> and rename <samp>zoneinfo-leaps</samp>
1427 href="https://www.cambridge.org/fr/academic/subjects/computer-science/computing-general-interest/calendrical-calculations-ultimate-edition-4th-edition">Calendrical
1442 effects cause clocks to tick slightly faster than on Earth.
1445 href='https://www.whitehouse.gov/wp-content/uploads/2024/04/Celestial-Time-Standardization-Policy.pdf'>ordered</a>
1472 It is divided into a conventional 24-hour clock, so each Mars second
1481 <a href="https://en.wikipedia.org/wiki/Airy-0">Airy-0</a>, named in
1505 sequential count of Mars solar days elapsed since about 1873-12-29
1512 On other planets, Sun-based time and calendars would work quite
1545 (2020-03-08).
1549 <em><a href="https://mitpress.mit.edu/books/making-time-mars">Making
1550 Time on Mars</a></em>, MIT Press (March 2020), ISBN 978-0262043854.
1553 Jia-Rui Chong,
1554 "<a href="https://www.latimes.com/archives/la-xpm-2004-jan-14-sci-marstime14-story.html">Workdays
1556 (2004-01-14), pp A1, A20–A21.
1560 "<a href="https://www.theatlantic.com/technology/archive/2015/02/jet-lag-is-worse-on-mars/386033/">Jet
1561 Lag Is Worse on Mars</a>", <cite>The Atlantic</cite> (2015-02-26)
1565 "<a href="https://www.universetoday.com/37481/days-of-the-planets/">How
1567 (2016-01-20).
1574 This file is in the public domain, so clarified as of 2009-05-17 by