date_trunc problems crossing DST border

[ PostgreSQL 7.4.5, Linux (Debian sarge) ]

The date_trunc function is making some off-by-one errors when working at
a DST border.

=> select date_trunc('minute', '2004-10-31 01:00:00-05'::timestamptz);
date_trunc
------------------------
2004-10-31 01:00:00-04

Expecting 2004-10-31 01:00:00-05, same error happens with minutes after
1 am. The timezone error also happens when truncating to minutes,
seconds, hours. I suspect this is happening because there are two
01:00:00 local time this day because of the "fall back" DST switch.

--
-Cheetah
"Reality is that which, when you stop believing in it, doesn't go away".
-- Philip K. Dick
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