date_trunc('week', '2005-01-01'::TIMESTAMP)

select date_trunc('week', '2005-01-01'::TIMESTAMP) returns '2006-01-02
00:00:00'

is this the intended result or is some kind of a bug ?
the result should not be '2004-12-27 00:00:00' ?

thanks,
Razvan Radu