Okla. Stat. tit. 12A, § 12A-3-108: Payable on Demand or at Definite Time

PAYABLE ON DEMAND OR AT DEFINITE TIME

(a) A promise or order is "payable on demand" if it (i) states

that it is payable on demand or at sight, or otherwise indicates

that it is payable at the will of the holder, or (ii) does not state

any time of payment.

(b) A promise or order is "payable at a definite time" if it is

payable on elapse of a definite period of time after sight or

acceptance or at a fixed date or dates or at a time or times readily

ascertainable at the time the promise or order is issued, subject to

rights of (i) prepayment, (ii) acceleration, (iii) extension at the

option of the holder, or (iv) extension to a further definite time

at the option of the maker or acceptor or automatically upon or

after a specified act or event.

(c) If an instrument, payable at a fixed date, is also payable

upon demand made before the fixed date, the instrument is payable on

demand until the fixed date and, if demand for payment is not made

before that date, becomes payable at a definite time on the fixed

date.