One consideration is null field processing. You need to use the ALWNULL keyword on the field in DDS and use RPG4's %NULLIND BIF to set the null indicator on or off. Unless, that is, you don't mind '01-01-0001' as a default date.
Where I work, we use 7-byte CYYMMDD fields for dates. I wrote some modules to do the conversion to or from 6 or 8 byte numeric fields for displaying and printing. "Don't worry about the world coming to an end today. It's already tomorrow in Australia."
--Charles Schultz