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- <!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.1. Date/Time Input Interpretation</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-appendix.html" title="Appendix B. Date/Time Support" /><link rel="next" href="datetime-invalid-input.html" title="B.2. Handling of Invalid or Ambiguous Timestamps" /></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.1. Date/Time Input Interpretation</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="datetime-appendix.html" title="Appendix B. Date/Time Support">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-invalid-input.html" title="B.2. Handling of Invalid or Ambiguous Timestamps">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="DATETIME-INPUT-RULES"><div class="titlepage"><div><div><h2 class="title" style="clear: both">B.1. Date/Time Input Interpretation</h2></div></div></div><p>
- Date/time input strings are decoded using the following procedure.
- </p><div class="procedure"><ol class="procedure" type="1"><li class="step"><p>
- Break the input string into tokens and categorize each token as
- a string, time, time zone, or number.
- </p><ol type="a" class="substeps"><li class="step"><p>
- If the numeric token contains a colon (<code class="literal">:</code>), this is
- a time string. Include all subsequent digits and colons.
- </p></li><li class="step"><p>
- If the numeric token contains a dash (<code class="literal">-</code>), slash
- (<code class="literal">/</code>), or two or more dots (<code class="literal">.</code>), this is
- a date string which might have a text month. If a date token has
- already been seen, it is instead interpreted as a time zone
- name (e.g., <code class="literal">America/New_York</code>).
- </p></li><li class="step"><p>
- If the token is numeric only, then it is either a single field
- or an ISO 8601 concatenated date (e.g.,
- <code class="literal">19990113</code> for January 13, 1999) or time
- (e.g., <code class="literal">141516</code> for 14:15:16).
- </p></li><li class="step"><p>
- If the token starts with a plus (<code class="literal">+</code>) or minus
- (<code class="literal">-</code>), then it is either a numeric time zone or a special
- field.
- </p></li></ol></li><li class="step"><p>
- If the token is an alphabetic string, match up with possible strings:
- </p><ol type="a" class="substeps"><li class="step"><p>
- See if the token matches any known time zone abbreviation.
- These abbreviations are supplied by the configuration file
- described in <a class="xref" href="datetime-config-files.html" title="B.4. Date/Time Configuration Files">Section B.4</a>.
- </p></li><li class="step"><p>
- If not found, search an internal table to match
- the token as either a special string (e.g., <code class="literal">today</code>),
- day (e.g., <code class="literal">Thursday</code>),
- month (e.g., <code class="literal">January</code>),
- or noise word (e.g., <code class="literal">at</code>, <code class="literal">on</code>).
- </p></li><li class="step"><p>
- If still not found, throw an error.
- </p></li></ol></li><li class="step"><p>
- When the token is a number or number field:
- </p><ol type="a" class="substeps"><li class="step"><p>
- If there are eight or six digits,
- and if no other date fields have been previously read, then interpret
- as a <span class="quote">“<span class="quote">concatenated date</span>”</span> (e.g.,
- <code class="literal">19990118</code> or <code class="literal">990118</code>).
- The interpretation is <code class="literal">YYYYMMDD</code> or <code class="literal">YYMMDD</code>.
- </p></li><li class="step"><p>
- If the token is three digits
- and a year has already been read, then interpret as day of year.
- </p></li><li class="step"><p>
- If four or six digits and a year has already been read, then
- interpret as a time (<code class="literal">HHMM</code> or <code class="literal">HHMMSS</code>).
- </p></li><li class="step"><p>
- If three or more digits and no date fields have yet been found,
- interpret as a year (this forces yy-mm-dd ordering of the remaining
- date fields).
- </p></li><li class="step"><p>
- Otherwise the date field ordering is assumed to follow the
- <code class="varname">DateStyle</code> setting: mm-dd-yy, dd-mm-yy, or yy-mm-dd.
- Throw an error if a month or day field is found to be out of range.
- </p></li></ol></li><li class="step"><p>
- 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 1 BC becomes year zero.)
- </p></li><li class="step"><p>
- If BC was not specified, and if the year field was two digits in length,
- then adjust the year to four digits. If the field is less than 70, then
- add 2000, otherwise add 1900.
-
- </p><div class="tip"><h3 class="title">Tip</h3><p>
- Gregorian years AD 1-99 can be entered by using 4 digits with leading
- zeros (e.g., <code class="literal">0099</code> is AD 99).
- </p></div><p>
- </p></li></ol></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="datetime-appendix.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-invalid-input.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Appendix B. Date/Time Support </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> B.2. Handling of Invalid or Ambiguous Timestamps</td></tr></table></div></body></html>
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