iconv is used to convert the date into into internal format i.e only datastage can understand

example :- date comming in mm/dd/yyyy format

datasatge will conver this ur date into some number like :- 740

u can use this 740 in derive in ur own format by using oconv.

suppose u want to change mm/dd/yyyy  to dd/mm/yyyy

now u will use iconv and oconv.

ocnv(iconv(datecommingfromi/pstring,SOMEXYZ(seein help which is iconvformat),defineoconvformat))