Question : Convert SQL datetime from UTC to local

I have a MS SQL database in which all datetimes are stored as UTC(GMT).  All work that this database keeps track of is in the EST time zone.  I need to make a stored procedure that can convert a given datetime to whatever the local time should be.  I've figured out how to do this with an offset and the DATEADD() function, but I dont know how to determine the appropriate offset for the datetime.  I could use this:

DATEADD(hour,DATEDIFF(hour,GETUTCDATE(),GETDATE()),@varDate)

but this calculates the offset based on the current time, which fails in the case where I am calculating a datetime from daylight savings at a time that isnt in daylight savings.

It seems like if I could seed GETDATE and GETUTCDATE with the date I am working with that would work, but I dont know how or if I can do that.

Thanks!

Answer : Convert SQL datetime from UTC to local

Link to a solution that has a downloadable database of timezones, in standard TIME_ZONE_INFORMATION structure.

http://www.codeproject.com/KB/database/ConvertUTCToLocal.aspx