(1):

(n.) A date put to a bill of exchange or other paper, later than that when it was actually made.

(2):

(a.) Made or done after the date assigned.

(3):

(v. t.) To date after the real time; as, to postdate a contract, that is, to date it later than the time when it was in fact made.

(4):

(v. t.) To affix a date to after the event.