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Diffstat (limited to 'doc/src/sgml/func.sgml')
| -rw-r--r-- | doc/src/sgml/func.sgml | 22 |
1 files changed, 13 insertions, 9 deletions
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml index a8d57f4e39a..aa235f139e3 100644 --- a/doc/src/sgml/func.sgml +++ b/doc/src/sgml/func.sgml @@ -9114,18 +9114,22 @@ SELECT (DATE '2001-10-30', DATE '2001-10-30') OVERLAPS When adding an <type>interval</type> value to (or subtracting an <type>interval</type> value from) a <type>timestamp with time zone</type> value, the days component advances or decrements the date of the - <type>timestamp with time zone</type> by the indicated number of days. + <type>timestamp with time zone</type> by the indicated number of days, + keeping the time of day the same. Across daylight saving time changes (when the session time zone is set to a time zone that recognizes DST), this means <literal>interval '1 day'</literal> does not necessarily equal <literal>interval '24 hours'</literal>. - For example, with the session time zone set to <literal>CST7CDT</literal>, - <literal>timestamp with time zone '2005-04-02 12:00-07' + interval '1 day'</literal> - will produce <literal>timestamp with time zone '2005-04-03 12:00-06'</literal>, - while adding <literal>interval '24 hours'</literal> to the same initial - <type>timestamp with time zone</type> produces - <literal>timestamp with time zone '2005-04-03 13:00-06'</literal>, as there is - a change in daylight saving time at <literal>2005-04-03 02:00</literal> in time zone - <literal>CST7CDT</literal>. + For example, with the session time zone set + to <literal>America/Denver</literal>: +<screen> +SELECT timestamp with time zone '2005-04-02 12:00:00-07' + interval '1 day'; +<lineannotation>Result: </lineannotation><computeroutput>2005-04-03 12:00:00-06</computeroutput> +SELECT timestamp with time zone '2005-04-02 12:00:00-07' + interval '24 hours'; +<lineannotation>Result: </lineannotation><computeroutput>2005-04-03 13:00:00-06</computeroutput> +</screen> + This happens because an hour was skipped due to a change in daylight saving + time at <literal>2005-04-03 02:00:00</literal> in time zone + <literal>America/Denver</literal>. </para> <para> |