Check out my post regarding dates in reporting services:
http://kamalhitari.blogspot.com/2008/02/working-with-dates-in-reporting.html
Also, if you want to add dates then the normal sql functions should work as normal. check this article for more info:
http://www.developer.com/db/article.php/3513996
To group fields and columns, you need to set in the report wizard when creating the report initially, i'm assuming you are using visual studio 2005 to do this.
Kamal Hitari
http://kamalhitari.blogspot.com