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2018-01-29

2018-01-29 16:45:57 by Henrik Grubbström (Grubba) <grubba@grubba.org>

Updated to 2018c.

52:   applications requiring accurate handling of all past times everywhere,   as it would take far too much effort and guesswork to record all   details of pre-1970 civil timekeeping. + Athough some information outside the scope of the database is + collected in a file <code>backzone</code> that is distributed along + with the database proper, this file is less reliable and does not + necessarily follow database guidelines.   </p>      <p>
240:   zone rules. It is intended to be an exhaustive list of names for   geographic regions as described above; this is a subset of the names   in the data. Although a '<code>zone1970.tab</code>' location's longitude - corresponds to its LMT offset with one hour for every 15 degrees east + corresponds to its LMT offset with one hour for every 15&deg; east   longitude, this relationship is not exact.   </p>   
279:   in decreasing order of importance:   <ul>    <li> -  Use three or more characters that are ASCII alphanumerics or +  Use three to six characters that are ASCII alphanumerics or    '<code>+</code>' or '<code>-</code>'.    Previous editions of this database also used characters like    '<code> </code>' and '<code>?</code>', but these
297:    '<code>+</code>' and '<code>-</code>' are safe in all locales.       In other words, in the C locale the POSIX extended regular -  expression <code>[-+[:alnum:]]{3,}</code> should match +  expression <code>[-+[:alnum:]]{3,6}</code> should match    the abbreviation.    This guarantees that all abbreviations could have been    specified by a POSIX TZ string.
308:    We assume that applications translate them to other languages    as part of the normal localization process; for example,    a French application might translate 'EST' to 'HNE'. +  + <p><small>These abbreviations (for standard/daylight/etc. time) are: + ACST/ACDT Australian Central, + AST/ADT/APT/AWT/ADDT Atlantic, + AEST/AEDT Australian Eastern, + AHST/AHDT Alaska-Hawaii, + AKST/AKDT Alaska, + AWST/AWDT Australian Western, + BST/BDT Bering, + CAT/CAST Central Africa, + CET/CEST/CEMT Central European, + ChST Chamorro, + CST/CDT/CWT/CPT/CDDT Central [North America], + CST/CDT China, + GMT/BST/IST/BDST Greenwich, + EAT East Africa, + EST/EDT/EWT/EPT/EDDT Eastern [North America], + EET/EEST Eastern European, + GST Guam, + HST/HDT Hawaii, + HKT/HKST Hong Kong, + IST India, + IST/GMT Irish, + IST/IDT/IDDT Israel, + JST/JDT Japan, + KST/KDT Korea, + MET/MEST Middle European (a backward-compatibility alias for Central European), + MSK/MSD Moscow, + MST/MDT/MWT/MPT/MDDT Mountain, + NST/NDT/NWT/NPT/NDDT Newfoundland, + NST/NDT/NWT/NPT Nome, + NZMT/NZST New Zealand through 1945, + NZST/NZDT New Zealand 1946&ndash;present, + PKT/PKST Pakistan, + PST/PDT/PWT/PPT/PDDT Pacific, + SAST South Africa, + SST Samoa, + WAT/WAST West Africa, + WET/WEST/WEMT Western European, + WIB Waktu Indonesia Barat, + WIT Waktu Indonesia Timur, + WITA Waktu Indonesia Tengah, + YST/YDT/YWT/YPT/YDDT Yukon</small>.</p>    </li>    <li>    For zones whose times are taken from a city's longitude, use the -  traditional <var>x</var>MT notation, e.g. 'PMT' for -  Paris Mean Time. -  The only name like this in current use is 'GMT'. + traditional <var>x</var>MT notation. The only abbreviation like this + in current use is 'GMT'. The others are for timestamps before 1960, + except that Monrovia Mean Time persisted until 1972. Typically, + numeric abbreviations (e.g., '<code>-</code>004430' for MMT) would + cause trouble here, as the numeric strings would exceed the POSIX length limit. +  + <p><small>These abbreviations are: + AMT Amsterdam, Asunción, Athens; + BMT Baghdad, Bangkok, Batavia, Bern, Bogotá, Bridgetown, Brussels, Bucharest; + CMT Calamarca, Caracas, Chisinau, Colón, Copenhagen, Córdoba; + DMT Dublin/Dunsink; + EMT Easter; + FFMT Fort-de-France; + FMT Funchal; + GMT Greenwich; + HMT Havana, Helsinki, Horta, Howrah; + IMT Irkutsk, Istanbul; + JMT Jerusalem; + KMT Kaunas, Kiev, Kingston; + LMT Lima, Lisbon, local, Luanda; + MMT Macassar, Madras, Malé, Managua, Minsk, Monrovia, Montevideo, Moratuwa, +  Moscow; + PLMT Phù Liễn; + PMT Paramaribo, Paris, Perm, Pontianak, Prague; + PMMT Port Moresby; + QMT Quito; + RMT Rangoon, Riga, Rome; + SDMT Santo Domingo; + SJMT San José; + SMT Santiago, Simferopol, Singapore, Stanley; + TBMT Tbilisi; + TMT Tallinn, Tehran; + WMT Warsaw</small>.</p> +  + <p><small>A few abbreviations also follow the pattern that + GMT/BST established for time in the UK. They are: +  + CMT/BST for Calamarca Mean Time and Bolivian Summer Time + 1890&ndash;1932, DMT/IST for Dublin/Dunsink Mean Time and Irish Summer Time + 1880&ndash;1916, MMT/MST/MDST for Moscow 1880&ndash;1919, and RMT/LST + for Riga Mean Time and Latvian Summer time 1880&ndash;1926. + An extra-special case is SET for Swedish Time (<em>svensk + normaltid</em>) 1879&ndash;1899, 3&deg; west of the Stockholm + Observatory.</small></p>    </li>    <li>    Use 'LMT' for local mean time of locations before the introduction
340:    history tends to use numeric abbreviations and a particular    entry could go either way, use a numeric abbreviation.    </li> - </ul> -  [The remaining guidelines predate the introduction of <code>%z</code>. -  They are problematic as they mean tz data entries invent -  notation rather than record it. These guidelines are now -  deprecated and the plan is to gradually move to <code>%z</code> for -  inhabited locations and to "<code>-</code>00" for uninhabited locations.] - <ul> +     <li> -  If there is no common English abbreviation, abbreviate the English -  translation of the usual phrase used by native speakers. -  If this is not available or is a phrase mentioning the country -  (e.g. "Cape Verde Time"), then: -  <ul> -  <li> -  When a country is identified with a single or principal zone, -  append 'T' to the country's ISO code, e.g. 'CVT' for -  Cape Verde Time. For summer time append 'ST'; -  for double summer time append 'DST'; etc. -  </li> -  <li> -  Otherwise, take the first three letters of an English place -  name identifying each zone and append 'T', 'ST', etc. -  as before; e.g. 'CHAST' for CHAtham Summer Time. -  </li> -  </ul> -  </li> -  <li> +     Use UT (with time zone abbreviation '<code>-</code>00') for    locations while uninhabited. The leading    '<code>-</code>' is a flag that the time
376:   </ul>   <p>   Application writers should note that these abbreviations are ambiguous - in practice: e.g. 'CST' has a different meaning in China than - it does in the United States. In new applications, it's often better - to use numeric UT offsets like '<code>-</code>0600' instead of time zone - abbreviations like 'CST'; this avoids the ambiguity. + in practice: e.g., 'CST' means one thing in China and something else + in North America, and 'IST' can refer to time in India, Ireland or + Israel. To avoid ambiguity, use numeric UT offsets like + '<code>-</code>0600' instead of time zone abbreviations like 'CST'.   </p>    </section>   
388:    <h2 id="accuracy">Accuracy of the tz database</h2>   <p>   The tz database is not authoritative, and it surely has errors. - Corrections are welcome and encouraged; see the file CONTRIBUTING. + Corrections are welcome and encouraged; see the file <code>CONTRIBUTING</code>.   Users requiring authoritative data should consult national standards   bodies and the references cited in the database's comments.   </p>
598:    and daylight saving time (DST) zone names.    Starting with POSIX.1-2001, <var>std</var>    and <var>dst</var> may also be -  in a quoted form like '<code>&lt;UTC+10&gt;</code>'; this allows +  in a quoted form like '<code>&lt;+09&gt;</code>'; this allows    "<code>+</code>" and "<code>-</code>" in the names.    </dd>    <dt><var>offset</var></dt><dd>
646:   </dd>   </dl>    Here is an example POSIX TZ string for New Zealand after 2007. -  It says that standard time (NZST) is 12 hours ahead of UTC, +  It says that standard time (NZST) is 12 hours ahead of UT,    and that daylight saving time (NZDT) is observed from September's    last Sunday at 02:00 until April's first Sunday at 03:00:   
678:    applications that an administrator wants used only at certain    times &ndash;    without regard to whether the user has fiddled the TZ environment -  variable. While an administrator can "do everything in UTC" to get +  variable. While an administrator can "do everything in UT" to get    around the problem, doing so is inconvenient and precludes handling    daylight saving time shifts - as might be required to limit phone    calls to off-peak hours.)
902:   recent releases. For example, tz data files typically do not rely on   recently-added <code>zic</code> features, so that users can run   older <code>zic</code> versions to process newer data - files. <a href="tz-link.htm">Sources for time zone and daylight + files. <a href="tz-link.html">Sources for time zone and daylight   saving time data</a> describes how   releases are tagged and distributed.   </p>
1003:   Michael Allison and Robert Schmunk,   "<a href="https://www.giss.nasa.gov/tools/mars24/help/notes.html">Technical   Notes on Mars Solar Time as Adopted by the Mars24 Sunclock</a>" - (2012-08-08). + (2015-06-30).    </li>    <li>   Jia-Rui Chong,