ধারা ২১BA note or bill payable at a determinable future time

21B. A promissory note or bill of exchange is payable at a determinable future time within the meaning of this Act if it is expressed to be payable-

(a) at a fixed time after date or sight; or

(b) on or at a fixed time after the occurrence of a specified event which is certain to happen, though the time of its happening may be uncertain.