The following bug has been logged online:

Bug reference: 1649
Logged by: Nicholas Vinen
Email address: hb (AT) pg (DOT) x256.org
PostgreSQL version: 8.0.1
Operating system: Gentoo Linux
Description: Date calculation year off-by-one error
Details:

This is definitely not right:

rt3=# SELECT date_trunc('week', timestamp with time zone '2005-01-02
00:00:00-7');
date_trunc
------------------------
2006-01-02 00:00:00-08
(1 row)

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TIP 9: the planner will ignore your desire to choose an index scan if your
joining column's datatypes do not match

"Nicholas Vinen" <hb (AT) x256 (DOT) com> writes:
Already fixed in 8.0.2.

regards, tom lane

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TIP 8: explain analyze is your friend