1123 lines
27 KiB
Plaintext
1123 lines
27 KiB
Plaintext
<!--
|
||
$Header: /cvsroot/pgsql/doc/src/sgml/datetime.sgml,v 2.27 2002/03/22 19:20:07 petere Exp $
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Date/time details
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||
-->
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||
|
||
<appendix id="datetime-appendix">
|
||
<title id="datetime-appendix-title">Date/Time Support</title>
|
||
|
||
<para>
|
||
<productname>PostgreSQL</productname> uses an internal heuristic
|
||
parser for all date/time support. Dates and times are input as
|
||
strings, and are broken up into distinct fields with a preliminary
|
||
determination of what kind of information may be in the
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||
field. Each field is interpreted and either assigned a numeric
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||
value, ignored, or rejected.
|
||
The parser contains internal lookup tables for all textual fields,
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||
including months, days of the week, and time
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||
zones.
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||
</para>
|
||
|
||
<para>
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||
This appendix includes information on the content of these
|
||
lookup tables and describes the steps used by the parser to decode
|
||
dates and times.
|
||
</para>
|
||
|
||
<sect1>
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||
<title>Date/Time Keywords</title>
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||
|
||
<para>
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||
<table tocentry="1">
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||
<title>Month Abbreviations</title>
|
||
<tgroup cols="2">
|
||
<thead>
|
||
<row>
|
||
<entry>Month</entry>
|
||
<entry>Abbreviations</entry>
|
||
</row>
|
||
</thead>
|
||
<tbody>
|
||
<row>
|
||
<entry>April</entry>
|
||
<entry>Apr</entry>
|
||
</row>
|
||
<row>
|
||
<entry>August</entry>
|
||
<entry>Aug</entry>
|
||
</row>
|
||
<row>
|
||
<entry>December</entry>
|
||
<entry>Dec</entry>
|
||
</row>
|
||
<row>
|
||
<entry>February</entry>
|
||
<entry>Feb</entry>
|
||
</row>
|
||
<row>
|
||
<entry>January</entry>
|
||
<entry>Jan</entry>
|
||
</row>
|
||
<row>
|
||
<entry>July</entry>
|
||
<entry>Jul</entry>
|
||
</row>
|
||
<row>
|
||
<entry>June</entry>
|
||
<entry>Jun</entry>
|
||
</row>
|
||
<row>
|
||
<entry>March</entry>
|
||
<entry>Mar</entry>
|
||
</row>
|
||
<row>
|
||
<entry>November</entry>
|
||
<entry>Nov</entry>
|
||
</row>
|
||
<row>
|
||
<entry>October</entry>
|
||
<entry>Oct</entry>
|
||
</row>
|
||
<row>
|
||
<entry>September</entry>
|
||
<entry>Sep, Sept</entry>
|
||
</row>
|
||
</tbody>
|
||
</tgroup>
|
||
</table>
|
||
|
||
<note>
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||
<para>
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||
The month <literal>May</literal> has no explicit abbreviation, for obvious reasons.
|
||
</para>
|
||
</note>
|
||
</para>
|
||
|
||
<para>
|
||
<table tocentry="1">
|
||
<title>Day of the Week Abbreviations</title>
|
||
<tgroup cols="2">
|
||
<thead>
|
||
<row>
|
||
<entry>Day</entry>
|
||
<entry>Abbreviation</entry>
|
||
</row>
|
||
</thead>
|
||
<tbody>
|
||
<row>
|
||
<entry>Sunday</entry>
|
||
<entry>Sun</entry>
|
||
</row>
|
||
<row>
|
||
<entry>Monday</entry>
|
||
<entry>Mon</entry>
|
||
</row>
|
||
<row>
|
||
<entry>Tuesday</entry>
|
||
<entry>Tue, Tues</entry>
|
||
</row>
|
||
<row>
|
||
<entry>Wednesday</entry>
|
||
<entry>Wed, Weds</entry>
|
||
</row>
|
||
<row>
|
||
<entry>Thursday</entry>
|
||
<entry>Thu, Thur, Thurs</entry>
|
||
</row>
|
||
<row>
|
||
<entry>Friday</entry>
|
||
<entry>Fri</entry>
|
||
</row>
|
||
<row>
|
||
<entry>Saturday</entry>
|
||
<entry>Sat</entry>
|
||
</row>
|
||
</tbody>
|
||
</tgroup>
|
||
</table>
|
||
</para>
|
||
|
||
<para>
|
||
<table tocentry="1">
|
||
<title><productname>PostgreSQL</productname> Field Modifiers</title>
|
||
<titleabbrev>Field Modifiers</titleabbrev>
|
||
<tgroup cols="2">
|
||
<thead>
|
||
<row>
|
||
<entry>Identifier</entry>
|
||
<entry>Description</entry>
|
||
</row>
|
||
</thead>
|
||
<tbody>
|
||
<row>
|
||
<entry><literal>ABSTIME</literal></entry>
|
||
<entry>Keyword ignored</entry>
|
||
</row>
|
||
<row>
|
||
<entry><literal>AM</literal></entry>
|
||
<entry>Time is before 12:00</entry>
|
||
</row>
|
||
<row>
|
||
<entry><literal>AT</literal></entry>
|
||
<entry>Keyword ignored</entry>
|
||
</row>
|
||
<row>
|
||
<entry><literal>JULIAN</>, <literal>JD</>, <literal>J</></entry>
|
||
<entry>Next field is Julian Day</entry>
|
||
</row>
|
||
<row>
|
||
<entry><literal>ON</literal></entry>
|
||
<entry>Keyword ignored</entry>
|
||
</row>
|
||
<row>
|
||
<entry><literal>PM</literal></entry>
|
||
<entry>Time is on or after after 12:00</entry>
|
||
</row>
|
||
<row>
|
||
<entry><literal>T</literal></entry>
|
||
<entry>Next field is time</entry>
|
||
</row>
|
||
</tbody>
|
||
</tgroup>
|
||
</table>
|
||
</para>
|
||
|
||
<para>
|
||
The keyword <literal>ABSTIME</literal> is ignored for historical
|
||
reasons; in very old releases of
|
||
<productname>PostgreSQL</productname> invalid <type>ABSTIME</type>
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||
fields were emitted as <literal>Invalid Abstime</literal>. This is no
|
||
longer the case however and this keyword will likely be dropped in
|
||
a future release.
|
||
</para>
|
||
</sect1>
|
||
|
||
<sect1 id="timezones">
|
||
<title>Time Zones</title>
|
||
|
||
<indexterm zone="timezones">
|
||
<primary>time zones</primary>
|
||
</indexterm>
|
||
|
||
<para>
|
||
<productname>PostgreSQL</productname> contains internal tabular
|
||
information for time zone decoding, since there is no *nix standard
|
||
system interface to provide access to general, cross-timezone
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||
information. The underlying OS <emphasis>is</emphasis> used to
|
||
provide time zone information for <emphasis>output</emphasis>, however.
|
||
</para>
|
||
|
||
<para>
|
||
The following table of time zones recognized by
|
||
<productname>PostgreSQL</productname> is organized by time
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||
zone offset from UTC, rather than alphabetically; this is intended
|
||
to facilitate
|
||
matching local usage with recognized abbreviations for cases where
|
||
these might differ.
|
||
|
||
<table tocentry="1">
|
||
<title><productname>PostgreSQL</productname> Recognized Time Zones</title>
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||
<titleabbrev>Time Zones</titleabbrev>
|
||
<tgroup cols="3">
|
||
<thead>
|
||
<row>
|
||
<entry>Time Zone</entry>
|
||
<entry>Offset from UTC</entry>
|
||
<entry>Description</entry>
|
||
</row>
|
||
</thead>
|
||
<tbody>
|
||
<row>
|
||
<entry>NZDT</entry>
|
||
<entry>+13:00</entry>
|
||
<entry>New Zealand Daylight Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>IDLE</entry>
|
||
<entry>+12:00</entry>
|
||
<entry>International Date Line, East</entry>
|
||
</row>
|
||
<row>
|
||
<entry>NZST</entry>
|
||
<entry>+12:00</entry>
|
||
<entry>New Zealand Standard Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>NZT</entry>
|
||
<entry>+12:00</entry>
|
||
<entry>New Zealand Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>AESST</entry>
|
||
<entry>+11:00</entry>
|
||
<entry>Australia Eastern Summer Standard Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>ACSST</entry>
|
||
<entry>+10:30</entry>
|
||
<entry>Central Australia Summer Standard Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>CADT</entry>
|
||
<entry>+10:30</entry>
|
||
<entry>Central Australia Daylight Savings Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>SADT</entry>
|
||
<entry>+10:30</entry>
|
||
<entry>South Australian Daylight Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>AEST</entry>
|
||
<entry>+10:00</entry>
|
||
<entry>Australia Eastern Standard Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>EAST</entry>
|
||
<entry>+10:00</entry>
|
||
<entry>East Australian Standard Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>GST</entry>
|
||
<entry>+10:00</entry>
|
||
<entry>Guam Standard Time, USSR Zone 9</entry>
|
||
</row>
|
||
<row>
|
||
<entry>LIGT</entry>
|
||
<entry>+10:00</entry>
|
||
<entry>Melbourne, Australia</entry>
|
||
</row>
|
||
<row>
|
||
<entry>SAST</entry>
|
||
<entry>+09:30</entry>
|
||
<entry>South Australia Standard Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>CAST</entry>
|
||
<entry>+09:30</entry>
|
||
<entry>Central Australia Standard Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>AWSST</entry>
|
||
<entry>+09:00</entry>
|
||
<entry>Australia Western Summer Standard Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>JST</entry>
|
||
<entry>+09:00</entry>
|
||
<entry>Japan Standard Time,USSR Zone 8</entry>
|
||
</row>
|
||
<row>
|
||
<entry>KST</entry>
|
||
<entry>+09:00</entry>
|
||
<entry>Korea Standard Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>MHT</entry>
|
||
<entry>+09:00</entry>
|
||
<entry>Kwajalein Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>WDT</entry>
|
||
<entry>+09:00</entry>
|
||
<entry>West Australian Daylight Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>MT</entry>
|
||
<entry>+08:30</entry>
|
||
<entry>Moluccas Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>AWST</entry>
|
||
<entry>+08:00</entry>
|
||
<entry>Australia Western Standard Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>CCT</entry>
|
||
<entry>+08:00</entry>
|
||
<entry>China Coastal Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>WADT</entry>
|
||
<entry>+08:00</entry>
|
||
<entry>West Australian Daylight Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>WST</entry>
|
||
<entry>+08:00</entry>
|
||
<entry>West Australian Standard Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>JT</entry>
|
||
<entry>+07:30</entry>
|
||
<entry>Java Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>ALMST</entry>
|
||
<entry>+07:00</entry>
|
||
<entry>Almaty Summer Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>WAST</entry>
|
||
<entry>+07:00</entry>
|
||
<entry>West Australian Standard Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>CXT</entry>
|
||
<entry>+07:00</entry>
|
||
<entry>Christmas (Island) Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>ALMT</entry>
|
||
<entry>+06:00</entry>
|
||
<entry>Almaty Time</entry>
|
||
</row>
|
||
<!--
|
||
Conflicts with China Coastal Time
|
||
<row>
|
||
<entry>CCT</entry>
|
||
<entry>+06:30</entry>
|
||
<entry>Cocos Island Time</entry>
|
||
</row>
|
||
-->
|
||
<row>
|
||
<entry>MAWT</entry>
|
||
<entry>+06:00</entry>
|
||
<entry>Mawson (Antarctica) Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>IOT</entry>
|
||
<entry>+05:00</entry>
|
||
<entry>Indian Chagos Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>MVT</entry>
|
||
<entry>+05:00</entry>
|
||
<entry>Maldives Island Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>TFT</entry>
|
||
<entry>+05:00</entry>
|
||
<entry>Kerguelen Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>AFT</entry>
|
||
<entry>+04:30</entry>
|
||
<entry>Afganistan Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>EAST</entry>
|
||
<entry>+04:00</entry>
|
||
<entry>Antananarivo Savings Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>MUT</entry>
|
||
<entry>+04:00</entry>
|
||
<entry>Mauritius Island Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>RET</entry>
|
||
<entry>+04:00</entry>
|
||
<entry>Reunion Island Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>SCT</entry>
|
||
<entry>+04:00</entry>
|
||
<entry>Mahe Island Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>IT</entry>
|
||
<entry>+03:30</entry>
|
||
<entry>Iran Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>EAT</entry>
|
||
<entry>+03:00</entry>
|
||
<entry>Antananarivo, Comoro Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>BT</entry>
|
||
<entry>+03:00</entry>
|
||
<entry>Baghdad Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>EETDST</entry>
|
||
<entry>+03:00</entry>
|
||
<entry>Eastern Europe Daylight Savings Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>HMT</entry>
|
||
<entry>+03:00</entry>
|
||
<entry>Hellas Mediterranean Time (?)</entry>
|
||
</row>
|
||
<row>
|
||
<entry>BDST</entry>
|
||
<entry>+02:00</entry>
|
||
<entry>British Double Standard Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>CEST</entry>
|
||
<entry>+02:00</entry>
|
||
<entry>Central European Savings Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>CETDST</entry>
|
||
<entry>+02:00</entry>
|
||
<entry>Central European Daylight Savings Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>EET</entry>
|
||
<entry>+02:00</entry>
|
||
<entry>Eastern Europe, USSR Zone 1</entry>
|
||
</row>
|
||
<row>
|
||
<entry>FWT</entry>
|
||
<entry>+02:00</entry>
|
||
<entry>French Winter Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>IST</entry>
|
||
<entry>+02:00</entry>
|
||
<entry>Israel Standard Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>MEST</entry>
|
||
<entry>+02:00</entry>
|
||
<entry>Middle Europe Summer Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>METDST</entry>
|
||
<entry>+02:00</entry>
|
||
<entry>Middle Europe Daylight Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>SST</entry>
|
||
<entry>+02:00</entry>
|
||
<entry>Swedish Summer Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>BST</entry>
|
||
<entry>+01:00</entry>
|
||
<entry>British Summer Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>CET</entry>
|
||
<entry>+01:00</entry>
|
||
<entry>Central European Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>DNT</entry>
|
||
<entry>+01:00</entry>
|
||
<entry><foreignphrase>Dansk Normal Tid</foreignphrase></entry>
|
||
</row>
|
||
<row>
|
||
<entry>FST</entry>
|
||
<entry>+01:00</entry>
|
||
<entry>French Summer Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>MET</entry>
|
||
<entry>+01:00</entry>
|
||
<entry>Middle Europe Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>MEWT</entry>
|
||
<entry>+01:00</entry>
|
||
<entry>Middle Europe Winter Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>MEZ</entry>
|
||
<entry>+01:00</entry>
|
||
<entry>Middle Europe Zone</entry>
|
||
</row>
|
||
<row>
|
||
<entry>NOR</entry>
|
||
<entry>+01:00</entry>
|
||
<entry>Norway Standard Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>SET</entry>
|
||
<entry>+01:00</entry>
|
||
<entry>Seychelles Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>SWT</entry>
|
||
<entry>+01:00</entry>
|
||
<entry>Swedish Winter Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>WETDST</entry>
|
||
<entry>+01:00</entry>
|
||
<entry>Western Europe Daylight Savings Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>GMT</entry>
|
||
<entry>+00:00</entry>
|
||
<entry>Greenwich Mean Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>UT</entry>
|
||
<entry>+00:00</entry>
|
||
<entry>Universal Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>UTC</entry>
|
||
<entry>+00:00</entry>
|
||
<entry>Universal Time, Coordinated</entry>
|
||
</row>
|
||
<row>
|
||
<entry>Z</entry>
|
||
<entry>+00:00</entry>
|
||
<entry>Same as UTC</entry>
|
||
</row>
|
||
<row>
|
||
<entry>ZULU</entry>
|
||
<entry>+00:00</entry>
|
||
<entry>Same as UTC</entry>
|
||
</row>
|
||
<row>
|
||
<entry>WET</entry>
|
||
<entry>+00:00</entry>
|
||
<entry>Western Europe</entry>
|
||
</row>
|
||
<row>
|
||
<entry>WAT</entry>
|
||
<entry>-01:00</entry>
|
||
<entry>West Africa Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>NDT</entry>
|
||
<entry>-02:30</entry>
|
||
<entry>Newfoundland Daylight Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>ADT</entry>
|
||
<entry>-03:00</entry>
|
||
<entry>Atlantic Daylight Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>AWT</entry>
|
||
<entry>-03:00</entry>
|
||
<entry>(unknown)</entry>
|
||
</row>
|
||
<row>
|
||
<entry>NFT</entry>
|
||
<entry>-03:30</entry>
|
||
<entry>Newfoundland Standard Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>NST</entry>
|
||
<entry>-03:30</entry>
|
||
<entry>Newfoundland Standard Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>AST</entry>
|
||
<entry>-04:00</entry>
|
||
<entry>Atlantic Standard Time (Canada)</entry>
|
||
</row>
|
||
<row>
|
||
<entry>ACST</entry>
|
||
<entry>-04:00</entry>
|
||
<entry>Atlantic/Porto Acre Summer Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>ACT</entry>
|
||
<entry>-05:00</entry>
|
||
<entry>Atlantic/Porto Acre Standard Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>EDT</entry>
|
||
<entry>-04:00</entry>
|
||
<entry>Eastern Daylight Time</entry>
|
||
</row>
|
||
<!--
|
||
<row>
|
||
<entry>ZP4</entry>
|
||
<entry>-04:00</entry>
|
||
<entry>GMT +4 hours</entry>
|
||
</row>
|
||
-->
|
||
<row>
|
||
<entry>CDT</entry>
|
||
<entry>-05:00</entry>
|
||
<entry>Central Daylight Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>EST</entry>
|
||
<entry>-05:00</entry>
|
||
<entry>Eastern Standard Time</entry>
|
||
</row>
|
||
<!--
|
||
<row>
|
||
<entry>ZP5</entry>
|
||
<entry>-05:00</entry>
|
||
<entry>GMT +5 hours</entry>
|
||
</row>
|
||
-->
|
||
<row>
|
||
<entry>CST</entry>
|
||
<entry>-06:00</entry>
|
||
<entry>Central Standard Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>MDT</entry>
|
||
<entry>-06:00</entry>
|
||
<entry>Mountain Daylight Time</entry>
|
||
</row>
|
||
<!--
|
||
<row>
|
||
<entry>ZP6</entry>
|
||
<entry>-06:00</entry>
|
||
<entry>GMT +6 hours</entry>
|
||
</row>
|
||
-->
|
||
<row>
|
||
<entry>MST</entry>
|
||
<entry>-07:00</entry>
|
||
<entry>Mountain Standard Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>PDT</entry>
|
||
<entry>-07:00</entry>
|
||
<entry>Pacific Daylight Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>AKDT</entry>
|
||
<entry>-08:00</entry>
|
||
<entry>Alaska Daylight Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>PST</entry>
|
||
<entry>-08:00</entry>
|
||
<entry>Pacific Standard Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>YDT</entry>
|
||
<entry>-08:00</entry>
|
||
<entry>Yukon Daylight Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>AKST</entry>
|
||
<entry>-09:00</entry>
|
||
<entry>Alaska Standard Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>HDT</entry>
|
||
<entry>-09:00</entry>
|
||
<entry>Hawaii/Alaska Daylight Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>YST</entry>
|
||
<entry>-09:00</entry>
|
||
<entry>Yukon Standard Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>AHST</entry>
|
||
<entry>-10:00</entry>
|
||
<entry>Alaska-Hawaii Standard Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>HST</entry>
|
||
<entry>-10:00</entry>
|
||
<entry>Hawaii Standard Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>CAT</entry>
|
||
<entry>-10:00</entry>
|
||
<entry>Central Alaska Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>NT</entry>
|
||
<entry>-11:00</entry>
|
||
<entry>Nome Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>IDLW</entry>
|
||
<entry>-12:00</entry>
|
||
<entry>International Date Line, West</entry>
|
||
</row>
|
||
</tbody>
|
||
</tgroup>
|
||
</table>
|
||
</para>
|
||
|
||
<sect2>
|
||
<title>Australian Time Zones</title>
|
||
|
||
<para>
|
||
Australian time zones and their naming variants
|
||
account for fully one quarter of all time zones in the
|
||
<productname>PostgreSQL</productname> time zone lookup table.
|
||
There are two naming conflicts with time zones commonly used
|
||
in the United States, <literal>CST</literal> and <literal>EST</literal>.
|
||
</para>
|
||
|
||
<para>
|
||
If the run-time option <literal>AUSTRALIAN_TIMEZONES</literal> is set
|
||
then <literal>CST</literal>, <literal>EST</literal>, and
|
||
<literal>SAT</literal> will be
|
||
interpreted as Australian timezone names. Without this option,
|
||
<literal>CST</literal> and <literal>EST</literal> are taken as
|
||
American timezone names, while <literal>SAT</literal> is interpreted as a
|
||
noise word indicating <literal>Saturday</literal>.
|
||
|
||
<table tocentry="1">
|
||
<title><productname>PostgreSQL</productname> Australian Time Zones</title>
|
||
<titleabbrev>Australian Time Zones</titleabbrev>
|
||
<tgroup cols="3">
|
||
<thead>
|
||
<row>
|
||
<entry>Time Zone</entry>
|
||
<entry>Offset from UTC</entry>
|
||
<entry>Description</entry>
|
||
</row>
|
||
</thead>
|
||
<tbody>
|
||
<row>
|
||
<entry>ACST</entry>
|
||
<entry>+09:30</entry>
|
||
<entry>Central Australia Standard Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>CST</entry>
|
||
<entry>+10:30</entry>
|
||
<entry>Australian Central Standard Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>EST</entry>
|
||
<entry>+10:00</entry>
|
||
<entry>Australian Eastern Standard Time</entry>
|
||
</row>
|
||
<row>
|
||
<entry>SAT</entry>
|
||
<entry>+09:30</entry>
|
||
<entry>South Australian Standard Time</entry>
|
||
</row>
|
||
</tbody>
|
||
</tgroup>
|
||
</table>
|
||
</para>
|
||
</sect2>
|
||
|
||
<sect2>
|
||
<title>Date/Time Input Interpretation</title>
|
||
|
||
<para>
|
||
The date/time types are all decoded using a common set of routines.
|
||
</para>
|
||
|
||
<procedure>
|
||
<title>Date/Time Input Interpretation</title>
|
||
|
||
<step>
|
||
<para>
|
||
Break the input string into tokens and categorize each token as
|
||
a string, time, time zone, or number.
|
||
</para>
|
||
|
||
<substeps>
|
||
<step>
|
||
<para>
|
||
If the numeric token contains a colon (":"), this is a time
|
||
string. Include all subsequent digits and colons.
|
||
</para>
|
||
</step>
|
||
|
||
<step>
|
||
<para>
|
||
If the numeric token contains a dash ("-"), slash ("/"), or
|
||
two or more dots ("."),
|
||
this is a date string which may have a text month.
|
||
</para>
|
||
</step>
|
||
|
||
<step>
|
||
<para>
|
||
If the token is numeric only, then it is either a single field
|
||
or an ISO-8601 concatenated date
|
||
(e.g. <literal>19990113</literal> for January 13, 1999)
|
||
or time (e.g. 141516 for 14:15:16).
|
||
</para>
|
||
</step>
|
||
<step>
|
||
<para>
|
||
If the token starts with a plus ("+") or minus ("-"),
|
||
then it is either a time zone or a special field.
|
||
</para>
|
||
</step>
|
||
</substeps>
|
||
</step>
|
||
|
||
<step>
|
||
<para>
|
||
If the token is a text string, match up with possible strings.
|
||
</para>
|
||
|
||
<substeps>
|
||
<step>
|
||
<para>
|
||
Do a binary-search table lookup for the token
|
||
as either a special string (e.g. <literal>today</literal>),
|
||
day (e.g. <literal>Thursday</literal>),
|
||
month (e.g. <literal>January</literal>),
|
||
or noise word (e.g. <literal>at</literal>, <literal>on</literal>).
|
||
</para>
|
||
<para>
|
||
Set field values and bit mask for fields.
|
||
For example, set year, month, day for <literal>today</literal>,
|
||
and additionally hour, minute, second for <literal>now</literal>.
|
||
</para>
|
||
</step>
|
||
|
||
<step>
|
||
<para>
|
||
If not found, do a similar binary-search table lookup to match
|
||
the token with a time zone.
|
||
</para>
|
||
</step>
|
||
|
||
<step>
|
||
<para>
|
||
If not found, throw an error.
|
||
</para>
|
||
</step>
|
||
</substeps>
|
||
</step>
|
||
|
||
<step>
|
||
<para>
|
||
The token is a number or number field.
|
||
</para>
|
||
|
||
<substeps>
|
||
<step>
|
||
<para>
|
||
If there are more than 4 digits,
|
||
and if no other date fields have been previously read, then interpret
|
||
as a <quote>concatenated date</quote> (e.g. <literal>19990118</literal>). 8
|
||
and 6 digits are interpreted as year, month, and day, while 7
|
||
and 5 digits are interpreted as year, day of year, respectively.
|
||
</para>
|
||
</step>
|
||
|
||
<step>
|
||
<para>
|
||
If the token is three digits
|
||
and a year has already been decoded, then interpret as day of year.
|
||
</para>
|
||
</step>
|
||
|
||
<step>
|
||
<para>
|
||
If four or six digits and a year has already been read, then
|
||
interpret as a time.
|
||
</para>
|
||
</step>
|
||
|
||
<step>
|
||
<para>
|
||
If four or more digits, then interpret as a year.
|
||
</para>
|
||
</step>
|
||
|
||
<step>
|
||
<para>
|
||
If in European date mode, and if the day field has not yet been read,
|
||
and if the value is less than or equal to 31, then interpret as a day.
|
||
</para>
|
||
</step>
|
||
|
||
<step>
|
||
<para>
|
||
If the month field has not yet been read,
|
||
and if the value is less than or equal to 12, then interpret as a month.
|
||
</para>
|
||
</step>
|
||
|
||
<step>
|
||
<para>
|
||
If the day field has not yet been read,
|
||
and if the value is less than or equal to 31, then interpret as a day.
|
||
</para>
|
||
</step>
|
||
|
||
<step>
|
||
<para>
|
||
If two digits or four or more digits, then interpret as a year.
|
||
</para>
|
||
</step>
|
||
|
||
<step>
|
||
<para>
|
||
Otherwise, throw an error.
|
||
</para>
|
||
</step>
|
||
</substeps>
|
||
</step>
|
||
|
||
<step>
|
||
<para>
|
||
If BC has been specified, negate the year and add one for
|
||
internal storage
|
||
(there is no year zero in the Gregorian calendar, so numerically
|
||
<literal>1BC</literal> becomes year zero).
|
||
</para>
|
||
</step>
|
||
|
||
<step>
|
||
<para>
|
||
If BC was not specified, and if the year field was two digits in length, then
|
||
adjust the year to 4 digits. If the field was less than 70, then add 2000;
|
||
otherwise, add 1900.
|
||
|
||
<tip>
|
||
<para>
|
||
Gregorian years 1-99AD may be entered by using 4 digits with leading
|
||
zeros (e.g. 0099 is 99AD). Previous versions of
|
||
<productname>PostgreSQL</productname> accepted years with three
|
||
digits and with single digits, but as of version 7.0 the rules have
|
||
been tightened up to reduce the possibility of ambiguity.
|
||
</para>
|
||
</tip>
|
||
</para>
|
||
</step>
|
||
</procedure>
|
||
</sect2>
|
||
</sect1>
|
||
|
||
<sect1 id="units-history">
|
||
<title>History of Units</title>
|
||
|
||
<note>
|
||
<para>
|
||
Contributed by Jos<6F> Soares (<email>jose@sferacarta.com</email>)
|
||
</para>
|
||
</note>
|
||
|
||
<para>
|
||
The Julian Day was invented by the French scholar
|
||
Joseph Justus Scaliger (1540-1609)
|
||
and probably takes its name from the Scaliger's father,
|
||
the Italian scholar Julius Caesar Scaliger (1484-1558).
|
||
Astronomers have used the Julian period to assign a unique number to
|
||
every day since 1 January 4713 BC. This is the so-called Julian Day
|
||
(JD). JD 0 designates the 24 hours from noon UTC on 1 January 4713 BC
|
||
to noon UTC on 2 January 4713 BC.
|
||
</para>
|
||
|
||
<para>
|
||
<quote>Julian Day</quote> is different from <quote>Julian Date</quote>.
|
||
|
||
The Julian calendar was introduced by Julius Caesar in 45 BC. It was
|
||
in common use until the 1582, when countries started changing to the
|
||
Gregorian calendar.
|
||
|
||
In the Julian calendar, the tropical year is approximated as 365 1/4
|
||
days = 365.25 days. This gives an error of about 1 day in
|
||
128 years.
|
||
The accumulating calendar error prompted Pope Gregory XIII
|
||
to reform the calendar in accordance with instructions
|
||
from the Council of Trent.
|
||
</para>
|
||
|
||
<para>
|
||
In the Gregorian calendar, the tropical year is approximated as
|
||
365 + 97 / 400 days = 365.2425 days. Thus it takes approximately 3300
|
||
years for the tropical year to shift one day with respect to the
|
||
Gregorian calendar.
|
||
</para>
|
||
|
||
<para>
|
||
The approximation 365+97/400 is achieved by having 97 leap years
|
||
every 400 years, using the following rules:
|
||
|
||
<simplelist>
|
||
<member>
|
||
Every year divisible by 4 is a leap year.
|
||
</member>
|
||
<member>
|
||
However, every year divisible by 100 is not a leap year.
|
||
</member>
|
||
<member>
|
||
However, every year divisible by 400 is a leap year after all.
|
||
</member>
|
||
</simplelist>
|
||
|
||
So, 1700, 1800, 1900, 2100, and 2200 are not leap years. But 1600,
|
||
2000, and 2400 are leap years.
|
||
|
||
By contrast, in the older Julian calendar only years divisible by 4 are leap years.
|
||
</para>
|
||
|
||
<para>
|
||
The papal bull of February 1582 decreed that 10 days should be dropped
|
||
from October 1582 so that 15 October should follow immediately after
|
||
4 October.
|
||
This was observed in Italy, Poland, Portugal, and Spain. Other Catholic
|
||
countries followed shortly after, but Protestant countries were
|
||
reluctant to change, and the Greek orthodox countries didn't change
|
||
until the start of this century.
|
||
|
||
The reform was observed by Great Britain and Dominions (including what is
|
||
now the USA) in 1752.
|
||
Thus 2 Sep 1752 was followed by 14 Sep 1752.
|
||
|
||
This is why Unix systems have <application>cal</application>
|
||
produce the following:
|
||
|
||
<programlisting>
|
||
% cal 9 1752
|
||
September 1752
|
||
S M Tu W Th F S
|
||
1 2 14 15 16
|
||
17 18 19 20 21 22 23
|
||
24 25 26 27 28 29 30
|
||
</programlisting>
|
||
</para>
|
||
|
||
<note>
|
||
<para>
|
||
SQL92 states that
|
||
<quote>Within the definition of a <quote>datetime literal</quote>,
|
||
the <quote>datetime value</quote>s are constrained by the
|
||
natural rules for dates and times
|
||
according to the Gregorian calendar</quote>.
|
||
Dates between 1752-09-03 and 1752-09-13, although eliminated in
|
||
some countries by Papal fiat, conform to
|
||
<quote>natural rules</quote> and are hence valid dates.
|
||
</para>
|
||
</note>
|
||
|
||
<para>
|
||
Different calendars have been developed in various parts of the
|
||
world, many predating the Gregorian system.
|
||
|
||
For example,
|
||
the beginnings of the Chinese calendar can be traced back to the 14th
|
||
century BC. Legend has it that the Emperor Huangdi invented the
|
||
calendar in 2637 BC.
|
||
|
||
The People's Republic of China uses the Gregorian calendar
|
||
for civil purposes. Chinese calendar is used for determining
|
||
festivals.
|
||
</para>
|
||
</sect1>
|
||
</appendix>
|
||
|
||
<!-- Keep this comment at the end of the file
|
||
Local variables:
|
||
mode:sgml
|
||
sgml-omittag:nil
|
||
sgml-shorttag:t
|
||
sgml-minimize-attributes:nil
|
||
sgml-always-quote-attributes:t
|
||
sgml-indent-step:1
|
||
sgml-indent-data:t
|
||
sgml-parent-document:nil
|
||
sgml-default-dtd-file:"./reference.ced"
|
||
sgml-exposed-tags:nil
|
||
sgml-local-catalogs:("/usr/lib/sgml/catalog")
|
||
sgml-local-ecat-files:nil
|
||
End:
|
||
-->
|