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Document that we deviate from ISO 8601 by not using 'T' on output.

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Per discussion, we should explain that we follow RFC 3339 and not really
the letter of the ISO 8601 spec for timestamp output format.  Mostly
Brendan Jurd's wording, though I tweaked it to clarify that we do take 'T'
on input.  Minor additional copy-editing and markup-tweaking, too.
This commit is contained in:
Tom Lane 2012-05-21 11:56:00 -04:00
parent f1f6737e15
commit 8be950f5c0
1 changed files with 29 additions and 16 deletions
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45
doc/src/sgml/datatype.sgml
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@ -2206,37 +2206,46 @@ January 8 04:05:06 1999 PST
</thead>
<tbody>
<row>
<entry>ISO</entry>
<entry>ISO 8601/SQL standard</entry>
<entry>1997-12-17 07:37:16-08</entry>
<entry><literal>ISO</literal></entry>
<entry>ISO 8601, SQL standard</entry>
<entry><literal>1997-12-17 07:37:16-08</literal></entry>
</row>
<row>
<entry>SQL</entry>
<entry><literal>SQL</literal></entry>
<entry>traditional style</entry>
<entry>12/17/1997 07:37:16.00 PST</entry>
<entry><literal>12/17/1997 07:37:16.00 PST</literal></entry>
</row>
<row>
<entry>POSTGRES</entry>
<entry><literal>Postgres</literal></entry>
<entry>original style</entry>
<entry>Wed Dec 17 07:37:16 1997 PST</entry>
<entry><literal>Wed Dec 17 07:37:16 1997 PST</literal></entry>
</row>
<row>
<entry>German</entry>
<entry><literal>German</literal></entry>
<entry>regional style</entry>
<entry>17.12.1997 07:37:16.00 PST</entry>
<entry><literal>17.12.1997 07:37:16.00 PST</literal></entry>
</row>
</tbody>
</tgroup>
</table>
<note>
<para>
ISO 8601 specifies the use of uppercase letter <literal>T</> to separate
the date and time. <productname>PostgreSQL</> accepts that format on
input, but on output it uses a space rather than <literal>T</>, as shown
above. This is for readability and for consistency with RFC 3339 as
well as some other database systems.
</para>
</note>
<para>
In the <acronym>SQL</acronym> and POSTGRES styles, day appears before
month if DMY field ordering has been specified, otherwise month appears
before day.
(See <xref linkend="datatype-datetime-input">
for how this setting also affects interpretation of input values.)
<xref linkend="datatype-datetime-output2-table"> shows an
example.
<xref linkend="datatype-datetime-output2-table"> shows examples.
</para>
<table id="datatype-datetime-output2-table">
@ -2253,29 +2262,33 @@ January 8 04:05:06 1999 PST
<row>
<entry><literal>SQL, DMY</></entry>
<entry><replaceable>day</replaceable>/<replaceable>month</replaceable>/<replaceable>year</replaceable></entry>
<entry>17/12/1997 15:37:16.00 CET</entry>
<entry><literal>17/12/1997 15:37:16.00 CET</literal></entry>
</row>
<row>
<entry><literal>SQL, MDY</></entry>
<entry><replaceable>month</replaceable>/<replaceable>day</replaceable>/<replaceable>year</replaceable></entry>
<entry>12/17/1997 07:37:16.00 PST</entry>
<entry><literal>12/17/1997 07:37:16.00 PST</literal></entry>
</row>
<row>
<entry><literal>Postgres, DMY</></entry>
<entry><replaceable>day</replaceable>/<replaceable>month</replaceable>/<replaceable>year</replaceable></entry>
<entry>Wed 17 Dec 07:37:16 1997 PST</entry>
<entry><literal>Wed 17 Dec 07:37:16 1997 PST</literal></entry>
</row>
</tbody>
</tgroup>
</table>
<para>
The date/time styles can be selected by the user using the
The date/time style can be selected by the user using the
<command>SET datestyle</command> command, the <xref
linkend="guc-datestyle"> parameter in the
<filename>postgresql.conf</filename> configuration file, or the
<envar>PGDATESTYLE</envar> environment variable on the server or
client. The formatting function <function>to_char</function>
client.
</para>
<para>
The formatting function <function>to_char</function>
(see <xref linkend="functions-formatting">) is also available as
a more flexible way to format date/time output.
</para>