Negotiable Instruments Law
Section 4. Determinable future time; what constitutes.-An instrument is payable at a determinable future time, within the meaning of this Act, which is expressed to be payable-
(a) At a fixed period after date or sight; or
(b) On or before a fixed or determinable future time specified therein; or
(c) On or at a fixed period after the occurrence of a specified event, which is certain to happen, though the time of happening be uncertain.
An instrument payable upon a contingency is not negotiable, and the happening of the event does not cure the defect.