Go to Books Online and read up on the DatePart, DateDiff and DateAdd functions and how to use them to take apart DATETIME columns.
Also look at Lynn Pettis' excellent summary of how to use them: http://www.sqlservercentral.com/blogs/lynnpettis/2009/03/25/some-common-date-routines/
Good luck,
Sigerson
"No pressure, no diamonds." - Thomas Carlyle