Updated for Permission assignment change 1/11/1006.
Ok, I'll bet that you are asking, What is a Global System UDF, right? By Global I mean that the UDF is available from any database on the server. By System I mean that the two part naming rule does not apply to this scalar function.
The UDF conversion from datetime to an ISO format Date string is not hard, but something I use every day.
No need to convert this char(8) return value to a datetime datatype as T-SQL will make the conversion for us, plus the ISO date format is independent of the DATEFORMAT setting.