*** a/src/backend/utils/adt/timestamp.c
--- b/src/backend/utils/adt/timestamp.c
***************
*** 3645,3650 **** timestamptz_age(PG_FUNCTION_ARGS)
--- 3645,3651 ----
  	{
  		/* form the symbolic difference */
  		fsec = fsec1 - fsec2;
+ 		tm->tm_gmtoff = tm1->tm_gmtoff - tm2->tm_gmtoff;
  		tm->tm_sec = tm1->tm_sec - tm2->tm_sec;
  		tm->tm_min = tm1->tm_min - tm2->tm_min;
  		tm->tm_hour = tm1->tm_hour - tm2->tm_hour;
***************
*** 3652,3657 **** timestamptz_age(PG_FUNCTION_ARGS)
--- 3653,3667 ----
  		tm->tm_mon = tm1->tm_mon - tm2->tm_mon;
  		tm->tm_year = tm1->tm_year - tm2->tm_year;
  
+ 		/*
+ 		 * Currently all the DST changes hour changes, so we can directly
+ 		 * add the DST difference to hours calculation.
+ 		 * 
+ 		 * The drawback in this approach is that, sometimes it may give
+ 		 * result as 24:00:00 instead of 1 day.
+ 		 */
+ 		tm->tm_hour += -(tm->tm_gmtoff / (MINS_PER_HOUR * SECS_PER_MINUTE));
+ 
  		/* flip sign if necessary... */
  		if (dt1 < dt2)
  		{