From b2b6548c79eb63faf1d0939893b3bf183d5410a1 Mon Sep 17 00:00:00 2001
From: Bruce Momjian <bruce@momjian.us>
Date: Sat, 30 Jul 2005 14:52:04 +0000
Subject: Please find attached diffs for documentation and simple regression
 tests for the new interval->day changes. I added tests for justify_hours()
 and justify_days() to interval.sql, as they take interval input and produce
 interval output. If there's a more appropriate place for them, please let me
 know.

Michael Glaesemann
---
 doc/src/sgml/func.sgml | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

(limited to 'doc/src')

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 5c6092e4245..55a5a63ae59 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -1,5 +1,5 @@
 <!--
-$PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.273 2005/07/29 14:46:56 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.274 2005/07/30 14:52:04 momjian Exp $
 PostgreSQL documentation
 -->
 
@@ -4903,6 +4903,24 @@ SELECT SUBSTRING('XY1234Z', 'Y*?([0-9]{1,3})');
    such pair.
   </para>
 
+  <para>
+   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. 
+   Across daylight saving time changes (with the session tiem zone 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>.
+  </para>
+
     <table id="operators-datetime-table">
      <title>Date/Time Operators</title>
 
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