Miss. Code § 21-29-313
Notwithstanding any other provision of Articles 1, 3 or 5, in the computation of membership service or prior service under the provisions of Articles 1, 3 and 5, the following schedule shall govern: ten (10) or more months of service during any fiscal year shall constitute a year of service; seven (7) months to nine (9) months, inclusive, three-quarters (3/4) of a year of service; four (4) months to six (6) months, inclusive, one-half (1/2) year of service; one (1) month to three (3) months, inclusive, one-quarter (1/4) of a year of service.
Benefits payable under the provisions of Articles 1, 3 and 5 that previously were made on the basis of full years of creditable service shall be computed on the basis of the fractional years of service as provided in this section beginning July 1, 1991.
Miss. Code § 21-29-313