check this out.

"Working with SQL Server Date/Time Variables (4 Parts)", by Gregory A. Larsen

http://www.databasejournal.com/features/mssql/article.php/2191631

http://www.databasejournal.com/features/mssql/article.php/2197931

http://www.databasejournal.com/features/mssql/article.php/2209321

http://www.databasejournal.com/features/mssql/article.php/2216011

yesim.