If the field in the file is definded as a date data type, you can do the following:
D DMYDATE S D DATFMT(*DMY)
D DATEFLDYMD S D INZ(D’2010-04-20′)
C EVAL DMYDATE = DATEFLDYMD
DMYDATE now has a value of 20/04/10. If you want to keep the four digit year, then the only thing I can think of would be to set up a data structure to strip out the month, day and year then rearrange them in the order you want.