I have written a lot of SQL that involved date conversions. But I may be on a project that is offsite, and do not have access to a library of routines, so I end up scratching my head and looking on the Internet.

Lots of folks have done excellent write-ups on Transact-SQL data conversions. Here is just one that I found useful by Manuj Bahl:

Date and Time Manipulation in SQL Server 2000