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diff --git a/doc/src/sgml/html/datetime-config-files.html b/doc/src/sgml/html/datetime-config-files.html new file mode 100644 index 0000000..c8b22e4 --- /dev/null +++ b/doc/src/sgml/html/datetime-config-files.html @@ -0,0 +1,98 @@ +<?xml version="1.0" encoding="UTF-8" standalone="no"?> +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>B.4. Date/Time Configuration Files</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="datetime-keywords.html" title="B.3. Date/Time Key Words" /><link rel="next" href="datetime-posix-timezone-specs.html" title="B.5. POSIX Time Zone Specifications" /></head><body id="docContent" class="container-fluid col-10"><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">B.4. Date/Time Configuration Files</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="datetime-keywords.html" title="B.3. Date/Time Key Words">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="datetime-appendix.html" title="Appendix B. Date/Time Support">Up</a></td><th width="60%" align="center">Appendix B. Date/Time Support</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 14.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="datetime-posix-timezone-specs.html" title="B.5. POSIX Time Zone Specifications">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="DATETIME-CONFIG-FILES"><div class="titlepage"><div><div><h2 class="title" style="clear: both">B.4. Date/Time Configuration Files</h2></div></div></div><a id="id-1.11.3.7.2" class="indexterm"></a><p> + Since timezone abbreviations are not well standardized, + <span class="productname">PostgreSQL</span> provides a means to customize + the set of abbreviations accepted by the server. The + <a class="xref" href="runtime-config-client.html#GUC-TIMEZONE-ABBREVIATIONS">timezone_abbreviations</a> run-time parameter + determines the active set of abbreviations. While this parameter + can be altered by any database user, the possible values for it + are under the control of the database administrator — they + are in fact names of configuration files stored in + <code class="filename">.../share/timezonesets/</code> of the installation directory. + By adding or altering files in that directory, the administrator + can set local policy for timezone abbreviations. + </p><p> + <code class="varname">timezone_abbreviations</code> can be set to any file name + found in <code class="filename">.../share/timezonesets/</code>, if the file's name + is entirely alphabetic. (The prohibition against non-alphabetic + characters in <code class="varname">timezone_abbreviations</code> prevents reading + files outside the intended directory, as well as reading editor + backup files and other extraneous files.) + </p><p> + A timezone abbreviation file can contain blank lines and comments + beginning with <code class="literal">#</code>. Non-comment lines must have one of + these formats: + +</p><pre class="synopsis"> +<em class="replaceable"><code>zone_abbreviation</code></em> <em class="replaceable"><code>offset</code></em> +<em class="replaceable"><code>zone_abbreviation</code></em> <em class="replaceable"><code>offset</code></em> D +<em class="replaceable"><code>zone_abbreviation</code></em> <em class="replaceable"><code>time_zone_name</code></em> +@INCLUDE <em class="replaceable"><code>file_name</code></em> +@OVERRIDE +</pre><p> + </p><p> + A <em class="replaceable"><code>zone_abbreviation</code></em> is just the abbreviation + being defined. An <em class="replaceable"><code>offset</code></em> is an integer giving + the equivalent offset in seconds from UTC, positive being east from + Greenwich and negative being west. For example, -18000 would be five + hours west of Greenwich, or North American east coast standard time. + <code class="literal">D</code> indicates that the zone name represents local + daylight-savings time rather than standard time. + </p><p> + Alternatively, a <em class="replaceable"><code>time_zone_name</code></em> can be given, referencing + a zone name defined in the IANA timezone database. The zone's definition + is consulted to see whether the abbreviation is or has been in use in + that zone, and if so, the appropriate meaning is used — that is, + the meaning that was currently in use at the timestamp whose value is + being determined, or the meaning in use immediately before that if it + wasn't current at that time, or the oldest meaning if it was used only + after that time. This behavior is essential for dealing with + abbreviations whose meaning has historically varied. It is also allowed + to define an abbreviation in terms of a zone name in which that + abbreviation does not appear; then using the abbreviation is just + equivalent to writing out the zone name. + </p><div class="tip"><h3 class="title">Tip</h3><p> + Using a simple integer <em class="replaceable"><code>offset</code></em> is preferred + when defining an abbreviation whose offset from UTC has never changed, + as such abbreviations are much cheaper to process than those that + require consulting a time zone definition. + </p></div><p> + The <code class="literal">@INCLUDE</code> syntax allows inclusion of another file in the + <code class="filename">.../share/timezonesets/</code> directory. Inclusion can be nested, + to a limited depth. + </p><p> + The <code class="literal">@OVERRIDE</code> syntax indicates that subsequent entries in the + file can override previous entries (typically, entries obtained from + included files). Without this, conflicting definitions of the same + timezone abbreviation are considered an error. + </p><p> + In an unmodified installation, the file <code class="filename">Default</code> contains + all the non-conflicting time zone abbreviations for most of the world. + Additional files <code class="filename">Australia</code> and <code class="filename">India</code> are + provided for those regions: these files first include the + <code class="literal">Default</code> file and then add or modify abbreviations as needed. + </p><p> + For reference purposes, a standard installation also contains files + <code class="filename">Africa.txt</code>, <code class="filename">America.txt</code>, etc, containing + information about every time zone abbreviation known to be in use + according to the IANA timezone database. The zone name + definitions found in these files can be copied and pasted into a custom + configuration file as needed. Note that these files cannot be directly + referenced as <code class="varname">timezone_abbreviations</code> settings, because of + the dot embedded in their names. + </p><div class="note"><h3 class="title">Note</h3><p> + If an error occurs while reading the time zone abbreviation set, no new + value is applied and the old set is kept. If the error occurs while + starting the database, startup fails. + </p></div><div class="caution"><h3 class="title">Caution</h3><p> + Time zone abbreviations defined in the configuration file override + non-timezone meanings built into <span class="productname">PostgreSQL</span>. + For example, the <code class="filename">Australia</code> configuration file defines + <code class="literal">SAT</code> (for South Australian Standard Time). When this + file is active, <code class="literal">SAT</code> will not be recognized as an abbreviation + for Saturday. + </p></div><div class="caution"><h3 class="title">Caution</h3><p> + If you modify files in <code class="filename">.../share/timezonesets/</code>, + it is up to you to make backups — a normal database dump + will not include this directory. + </p></div></div><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navfooter"><hr></hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="datetime-keywords.html" title="B.3. Date/Time Key Words">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="datetime-appendix.html" title="Appendix B. Date/Time Support">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="datetime-posix-timezone-specs.html" title="B.5. POSIX Time Zone Specifications">Next</a></td></tr><tr><td width="40%" align="left" valign="top">B.3. Date/Time Key Words </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 14.5 Documentation">Home</a></td><td width="40%" align="right" valign="top"> B.5. <acronym xmlns="http://www.w3.org/1999/xhtml" class="acronym">POSIX</acronym> Time Zone Specifications</td></tr></table></div></body></html>
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