(a) On and after July 1, 1980, no employer shall employ any of his employees for a workweek longer than forty hours, unless such employee receives compensation for his employment in excess of the hours above specified at a rate of not less than one and one-half times the regular rate at which he is employed.
(b) As used in this section the "regular rate" at which an employee is employed shall be deemed to include all remuneration for employment paid to, or on behalf of, the employee, but shall not be deemed to include:
(1) Sums paid as gifts; payments in the nature of gifts made at Christmas time or on other special occasions, as a reward for service, the amounts of which are not measured by or dependent on hours worked, production, or efficiency;