N.Y. Comp. Codes R. & Regs. tit. 2, § 328.1 – Background.

(a) Subparagraphs (b) and (d) of section 41(i)(1) and 341(i)(1) of the Retirement and Social Security Law, hereinafter referred to as subparagraphs (b) and subparagraphs (d), provide that time during which a member of the Retirement System is on an official leave of absence without pay from his or her position may be included in the computation of member service and final average salary. Subparagraphs (b) provide that the time spent on such a leave may be so included only if the head of the department in which such member is employed, and the State Comptroller, allow such time for retirement purposes at the time such leave is granted. Subparagraphs (d) provide that the time spent on certain specified types of such leave may be so included only if:
1. (1) the leave is granted for not more than two years;
2. (2) the State Comptroller allows inclusion of such time for retirement purposes at the time such leave is granted; and
3. (3) certain required payments are made to the Retirement System.
(b) The purpose of these provisions of law is to permit Retirement System members, under certain circumstances and with the express prior approvals noted above, to leave the service of the State or a participating employer temporarily, and continue to accrue retirement credit during such leave, since the experience and training gained as a result thereof will be of benefit to the State or participating employer upon the employee member's return to public service. The granting of such credits during the time spent on such leaves is contingent upon the employee member's actual return to service with the State or the participating employer and to the actual performance of the duties of his or her position.
(c) This regulation is promulgated to establish the guidelines applicable in granting credit for service and final average salary for the period of an authorized leave of absence without pay.