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  1. <?xml version="1.0" encoding="UTF-8" standalone="no"?>

  2. <!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 V1.79.1" /><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><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 12.4 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>

  3.     Since timezone abbreviations are not well standardized,

  4.     <span class="productname">PostgreSQL</span> provides a means to customize

  5.     the set of abbreviations accepted by the server.  The

  6.     <a class="xref" href="runtime-config-client.html#GUC-TIMEZONE-ABBREVIATIONS">timezone_abbreviations</a> run-time parameter

  7.     determines the active set of abbreviations.  While this parameter

  8.     can be altered by any database user, the possible values for it

  9.     are under the control of the database administrator — they

  10.     are in fact names of configuration files stored in

  11.     <code class="filename">.../share/timezonesets/</code> of the installation directory.

  12.     By adding or altering files in that directory, the administrator

  13.     can set local policy for timezone abbreviations.

  14.    </p><p>

  15.     <code class="varname">timezone_abbreviations</code> can be set to any file name

  16.     found in <code class="filename">.../share/timezonesets/</code>, if the file's name

  17.     is entirely alphabetic.  (The prohibition against non-alphabetic

  18.     characters in <code class="varname">timezone_abbreviations</code> prevents reading

  19.     files outside the intended directory, as well as reading editor

  20.     backup files and other extraneous files.)

  21.    </p><p>

  22.     A timezone abbreviation file can contain blank lines and comments

  23.     beginning with <code class="literal">#</code>.  Non-comment lines must have one of

  24.     these formats:

  25. 

  26. </p><pre class="synopsis">

  27. <em class="replaceable"><code>zone_abbreviation</code></em> <em class="replaceable"><code>offset</code></em>

  28. <em class="replaceable"><code>zone_abbreviation</code></em> <em class="replaceable"><code>offset</code></em> D

  29. <em class="replaceable"><code>zone_abbreviation</code></em> <em class="replaceable"><code>time_zone_name</code></em>

  30. @INCLUDE <em class="replaceable"><code>file_name</code></em>

  31. @OVERRIDE

  32. </pre><p>

  33.    </p><p>

  34.     A <em class="replaceable"><code>zone_abbreviation</code></em> is just the abbreviation

  35.     being defined.  An <em class="replaceable"><code>offset</code></em> is an integer giving

  36.     the equivalent offset in seconds from UTC, positive being east from

  37.     Greenwich and negative being west.  For example, -18000 would be five

  38.     hours west of Greenwich, or North American east coast standard time.

  39.     <code class="literal">D</code> indicates that the zone name represents local

  40.     daylight-savings time rather than standard time.

  41.    </p><p>

  42.     Alternatively, a <em class="replaceable"><code>time_zone_name</code></em> can be given, referencing

  43.     a zone name defined in the IANA timezone database.  The zone's definition

  44.     is consulted to see whether the abbreviation is or has been in use in

  45.     that zone, and if so, the appropriate meaning is used — that is,

  46.     the meaning that was currently in use at the timestamp whose value is

  47.     being determined, or the meaning in use immediately before that if it

  48.     wasn't current at that time, or the oldest meaning if it was used only

  49.     after that time.  This behavior is essential for dealing with

  50.     abbreviations whose meaning has historically varied.  It is also allowed

  51.     to define an abbreviation in terms of a zone name in which that

  52.     abbreviation does not appear; then using the abbreviation is just

  53.     equivalent to writing out the zone name.

  54.    </p><div class="tip"><h3 class="title">Tip</h3><p>

  55.      Using a simple integer <em class="replaceable"><code>offset</code></em> is preferred

  56.      when defining an abbreviation whose offset from UTC has never changed,

  57.      as such abbreviations are much cheaper to process than those that

  58.      require consulting a time zone definition.

  59.     </p></div><p>

  60.     The <code class="literal">@INCLUDE</code> syntax allows inclusion of another file in the

  61.     <code class="filename">.../share/timezonesets/</code> directory.  Inclusion can be nested,

  62.     to a limited depth.

  63.    </p><p>

  64.     The <code class="literal">@OVERRIDE</code> syntax indicates that subsequent entries in the

  65.     file can override previous entries (typically, entries obtained from

  66.     included files).  Without this, conflicting definitions of the same

  67.     timezone abbreviation are considered an error.

  68.    </p><p>

  69.     In an unmodified installation, the file <code class="filename">Default</code> contains

  70.     all the non-conflicting time zone abbreviations for most of the world.

  71.     Additional files <code class="filename">Australia</code> and <code class="filename">India</code> are

  72.     provided for those regions: these files first include the

  73.     <code class="literal">Default</code> file and then add or modify abbreviations as needed.

  74.    </p><p>

  75.     For reference purposes, a standard installation also contains files

  76.     <code class="filename">Africa.txt</code>, <code class="filename">America.txt</code>, etc, containing

  77.     information about every time zone abbreviation known to be in use

  78.     according to the IANA timezone database.  The zone name

  79.     definitions found in these files can be copied and pasted into a custom

  80.     configuration file as needed.  Note that these files cannot be directly

  81.     referenced as <code class="varname">timezone_abbreviations</code> settings, because of

  82.     the dot embedded in their names.

  83.    </p><div class="note"><h3 class="title">Note</h3><p>

  84.      If an error occurs while reading the time zone abbreviation set, no new

  85.      value is applied and the old set is kept. If the error occurs while

  86.      starting the database, startup fails.

  87.     </p></div><div class="caution"><h3 class="title">Caution</h3><p>

  88.      Time zone abbreviations defined in the configuration file override

  89.      non-timezone meanings built into <span class="productname">PostgreSQL</span>.

  90.      For example, the <code class="filename">Australia</code> configuration file defines

  91.      <code class="literal">SAT</code> (for South Australian Standard Time).  When this

  92.      file is active, <code class="literal">SAT</code> will not be recognized as an abbreviation

  93.      for Saturday.

  94.     </p></div><div class="caution"><h3 class="title">Caution</h3><p>

  95.      If you modify files in <code class="filename">.../share/timezonesets/</code>,

  96.      it is up to you to make backups — a normal database dump

  97.      will not include this directory.

  98.     </p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="datetime-keywords.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="datetime-appendix.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="datetime-posix-timezone-specs.html">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">Home</a></td><td width="40%" align="right" valign="top"> B.5. <acronym class="acronym">POSIX</acronym> Time Zone Specifications</td></tr></table></div></body></html>
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