Earnings, methods of calculating earnings and rate of earnings, including contractually fixed rates, and the minimum amount upon which earnings shall be paid shall be determined by the board of directors, and earnings shall be distributed on savings accounts at such times and in such manner and on such terms as may be prescribed by regulations of the director of the division of finance. The director’s regulations may permit the determination and declaration of rates of earnings during the month preceding the beginning of the period to which the rates are to apply, may provide for a determination date for computing earnings, and may authorize distribution of earnings on withdrawals between earning distribution dates. He may provide that an association may calculate, determine, and pay earnings upon any basis available to a federal association.