</indexterm>
<para>
- The <literal>AT TIME ZONE</literal> construct allows conversions
- of time stamps to different time zones. <xref
- linkend="functions-datetime-zoneconvert-table"/> shows its
- variants.
+ The <literal>AT TIME ZONE</literal> converts time
+ stamp <emphasis>without time zone</emphasis> to/from
+ time stamp <emphasis>with time zone</emphasis>, and
+ <emphasis>time</emphasis> values to different time zones. <xref
+ linkend="functions-datetime-zoneconvert-table"/> shows its variants.
</para>
<table id="functions-datetime-zoneconvert-table">
<para>
In these expressions, the desired time zone <replaceable>zone</replaceable> can be
- specified either as a text string (e.g., <literal>'PST'</literal>)
+ specified either as a text string (e.g., <literal>'America/Los_Angeles'</literal>)
or as an interval (e.g., <literal>INTERVAL '-08:00'</literal>).
In the text case, a time zone name can be specified in any of the ways
described in <xref linkend="datatype-timezones"/>.
</para>
<para>
- Examples (assuming the local time zone is <literal>PST8PDT</literal>):
+ Examples (assuming the local time zone is <literal>America/Los_Angeles</literal>):
<screen>
-SELECT TIMESTAMP '2001-02-16 20:38:40' AT TIME ZONE 'MST';
+SELECT TIMESTAMP '2001-02-16 20:38:40' AT TIME ZONE 'America/Denver';
<lineannotation>Result: </lineannotation><computeroutput>2001-02-16 19:38:40-08</computeroutput>
-SELECT TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40-05' AT TIME ZONE 'MST';
+SELECT TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40-05' AT TIME ZONE 'America/Denver';
<lineannotation>Result: </lineannotation><computeroutput>2001-02-16 18:38:40</computeroutput>
+
+SELECT TIMESTAMP '2001-02-16 20:38:40-05' AT TIME ZONE 'Asia/Tokyo' AT TIME ZONE 'America/Chicago';
+<lineannotation>Result: </lineannotation><computeroutput>2001-02-16 05:38:40</computeroutput>
</screen>
- The first example takes a time stamp without time zone and interprets it as MST time
- (UTC-7), which is then converted to PST (UTC-8) for display. The second example takes
- a time stamp specified in EST (UTC-5) and converts it to local time in MST (UTC-7).
+ The first example adds a time zone to a value that lacks it, and
+ displays the value using the current <varname>TimeZone</varname>
+ setting. The second example shifts the time stamp with time zone value
+ to the specified time zone, and returns the value without a time zone.
+ This allows storage and display of values different from the current
+ <varname>TimeZone</varname> setting. The third example converts
+ Tokyo time to Chicago time. Converting <emphasis>time</emphasis>
+ values to other time zones uses the currently active time zone rules
+ since no date is supplied.
</para>
<para>