California Code, Welfare and Institutions Code - WIC § 10826

(a) Each recipient of aid will be assigned a date or dates within the month as the date or dates on which he will be paid in subsequent months;

(b) Each warrant will be placed in the mail in order to be delivered on the assigned payment date and that in the event there is no mail delivery on the assigned payment date, the warrant will be placed in the mail in time to be delivered to the payee on the last mail delivery date prior to the payment date;  and

(c) Upon changing payment dates for any recipient, the recipient will receive a pro rata payment on the old payment date in payment of the aid to which such recipient is entitled prior to the new payment date.