Below is a script you can use to backup a database and include a date and time stamp on the file name.
DECLARE @backdate varchar(20)
set @backdate = (select REPLACE(REPLACE(CONVERT(varchar(100), GETDATE(), 100),’:’,’_’),’ ‘,’_’))
exec (‘BACKUP DATABASE [DatabaseName] TO DISK = N”c:\Program Files\Microsoft SQL Server\MSSQL\BACKUP\databaseName_’ + @backdate + ‘.bak” WITH INIT , NOUNLOAD , NAME = N”Database Name backup”, SKIP , STATS = 10, FORMAT’)
The date and time stamp will look like this: Dec_14_2009_12_00PM
You can use this to append on the file if you need to keep multiple copies of your .bak file.