Extract (week from date ) bug.

I think there must be a bug in the date calculations.
Consider the following query

select extract(week from date('2010-12-31')),  extract(week from date('2011=
-01-01')), extract(week from date('2011-01-03'))

Result:
date_part date_part date_part
52                     52               1


Why is extract(week from date('2011-01-01')) not identified as week 1?

-- Ubold Hooper
Amplify Insight| 55 Washington St. Brooklyn, NY. 11201|Tel: 347-474-4829|Em=
ail: uhooper@amplify.com<mailto:uhooper@amplify.com>