</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</> 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</>):

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>