January 1 2010 Will Fall On Which Week Of The Year?

1.
from http://www.google.com/support/forum/p/Calendar/thread?tid=71c18574c6d28dbd&hl=en ,
The Week Numbers calendar (found in Interesting calendars) is correct. It works off international date and time standards set forth by ISO 8601. The formal ISO definition indicates that week 01 is the week with the year's first Thursday in it (there are other equivalent descriptions for week 01, such as the week that contains 4 January, but I won't list them all here). Hope this clears things up.
However, select
DATEPART(wk, '2010-January-01') returns 1
2. The convention, becoming more common, to start calendar weeks on Monday

Interesting questions and analysis too, you learn new each day [].