For the purpose of calculating retirement allowances, credit for service rendered on a part-time basis in each fiscal year shall be based on the ratio that the service rendered bears:
(a)
To one academic year if rendered on an academic year basis, for members employed by the University of California, the California State University system, or school employees who are certificated members, under terms and conditions prescribed by the board.
(b)
To 10 months if rendered on a monthly basis.
(c)
To 215 days if the service was rendered after June 30, 1951, or to 250 days if the service was rendered prior to July 1, 1951, for services rendered on a daily basis.
(d)
To 1,720 hours if the service was rendered after June 30, 1951, or to 2,000 hours if the service was rendered prior to July 1, 1951, for service rendered on an hourly basis.