Index: timestamp.c
===================================================================
RCS file: /cvsroot/pgsql/src/backend/utils/adt/timestamp.c,v
retrieving revision 1.141
diff -c -c -r1.141 timestamp.c
*** timestamp.c	22 Jul 2005 19:00:54 -0000	1.141
--- timestamp.c	23 Jul 2005 02:00:07 -0000
***************
*** 3922,3938 ****
  }
  
  
! /* timestamp_zone()
!  * Encode timestamp type with specified time zone.
!  * Returns timestamp with time zone, with the input
   *	rotated from local time to the specified zone.
   */
  Datum
  timestamp_zone(PG_FUNCTION_ARGS)
  {
  	text	   *zone = PG_GETARG_TEXT_P(0);
  	Timestamp timestamp = PG_GETARG_TIMESTAMP(1);
! 	Timestamp result;
  	int			tz;
  	pg_tz      *tzp;
  	char        tzname[TZ_STRLEN_MAX+1];
--- 3922,3942 ----
  }
  
  
! /* 	timestamp_zone()
!  * 	Encode timestamp type with specified time zone.
!  * 	Returns timestamp with time zone, with the input
   *	rotated from local time to the specified zone.
+  *	This function is tricky because instead of shifting
+  *	the time _to_ a new time zone, it sets the time to _be_
+  *	the specified timezone.  This requires trickery
+  *	of double-subtracting the requested timezone offset.
   */
  Datum
  timestamp_zone(PG_FUNCTION_ARGS)
  {
  	text	   *zone = PG_GETARG_TEXT_P(0);
  	Timestamp timestamp = PG_GETARG_TIMESTAMP(1);
! 	TimestampTz	result;
  	int			tz;
  	pg_tz      *tzp;
  	char        tzname[TZ_STRLEN_MAX+1];
***************
*** 3960,3966 ****
  
  	/* Apply the timezone change */
  	if (timestamp2tm(timestamp, &tz, &tm, &fsec, NULL, tzp) != 0 ||
! 	    tm2timestamp(&tm, fsec, NULL, &result) != 0)
  	{
  		ereport(ERROR,
  				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
--- 3964,3970 ----
  
  	/* Apply the timezone change */
  	if (timestamp2tm(timestamp, &tz, &tm, &fsec, NULL, tzp) != 0 ||
! 	    tm2timestamp(&tm, fsec, &tz, &result) != 0)
  	{
  		ereport(ERROR,
  				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
***************
*** 3968,3974 ****
  				        tzname)));
  		PG_RETURN_NULL();
  	}
! 	PG_RETURN_TIMESTAMPTZ(timestamp2timestamptz(result));
  }
  
  /* timestamp_izone()
--- 3972,3981 ----
  				        tzname)));
  		PG_RETURN_NULL();
  	}
! 	/* Must double-adjust for timezone */
! 	result = dt2local(result, -tz);
! 
! 	PG_RETURN_TIMESTAMPTZ(result);
  }
  
  /* timestamp_izone()
Index: func.sgml
===================================================================
RCS file: /cvsroot/pgsql/doc/src/sgml/func.sgml,v
retrieving revision 1.268
retrieving revision 1.269
diff -c -c -r1.268 -r1.269
*** func.sgml	20 Jul 2005 16:42:29 -0000	1.268
--- func.sgml	22 Jul 2005 21:16:14 -0000	1.269
***************
*** 5693,5699 ****
           <literal><type>timestamp without time zone</type> AT TIME ZONE <replaceable>zone</></literal>
          </entry>
          <entry><type>timestamp with time zone</type></entry>
!         <entry>Convert local time in given time zone to UTC</entry>
         </row>
  
         <row>
--- 5693,5699 ----
           <literal><type>timestamp without time zone</type> AT TIME ZONE <replaceable>zone</></literal>
          </entry>
          <entry><type>timestamp with time zone</type></entry>
!         <entry>Treat given timestamp <emphasis>without time zone</> as located in the specified time zone</entry>
         </row>
  
         <row>
***************
*** 5701,5707 ****
           <literal><type>timestamp with time zone</type> AT TIME ZONE <replaceable>zone</></literal>
          </entry>
          <entry><type>timestamp without time zone</type></entry>
!         <entry>Convert UTC to local time in given time zone</entry>
         </row>
  
         <row>
--- 5701,5707 ----
           <literal><type>timestamp with time zone</type> AT TIME ZONE <replaceable>zone</></literal>
          </entry>
          <entry><type>timestamp without time zone</type></entry>
!         <entry>Convert given timestamp <emphasis>with time zone</> to the new time zone</entry>
         </row>
  
         <row>
***************
*** 5709,5715 ****
           <literal><type>time with time zone</type> AT TIME ZONE <replaceable>zone</></literal>
          </entry>
          <entry><type>time with time zone</type></entry>
!         <entry>Convert local time across time zones</entry>
         </row>
        </tbody>
       </tgroup>
--- 5709,5715 ----
           <literal><type>time with time zone</type> AT TIME ZONE <replaceable>zone</></literal>
          </entry>
          <entry><type>time with time zone</type></entry>
!         <entry>Convert given time <emphasis>with time zone</> to the new time zone</entry>
         </row>
        </tbody>
       </tgroup>
***************
*** 5720,5726 ****
      specified either as a text string (e.g., <literal>'PST'</literal>)
      or as an interval (e.g., <literal>INTERVAL '-08:00'</literal>).
      In the text case, the available zone names are those shown in
!     <xref linkend="datetime-timezone-set-table">.
     </para>
  
     <para>
--- 5720,5727 ----
      specified either as a text string (e.g., <literal>'PST'</literal>)
      or as an interval (e.g., <literal>INTERVAL '-08:00'</literal>).
      In the text case, the available zone names are those shown in
!     <xref linkend="datetime-timezone-set-table">.  The time zone can
!     also be implied using the default time zone for that session.
     </para>
  
     <para>
***************
*** 5732,5741 ****
  SELECT TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40-05' AT TIME ZONE 'MST';
  <lineannotation>Result: </lineannotation><computeroutput>2001-02-16 18:38:40</computeroutput>
  </screen>
!     The first example takes a zone-less time stamp and interprets it as MST time
!     (UTC-7) to produce a UTC time stamp, which is then rotated 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).
     </para>
  
     <para>
--- 5733,5741 ----
  SELECT TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40-05' AT TIME ZONE 'MST';
  <lineannotation>Result: </lineannotation><computeroutput>2001-02-16 18:38:40</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).
     </para>
  
     <para>