(a) With respect to service rendered prior to the date of membership, each employee who, pursuant to subsection 457(a) of this title, became a member of the retirement system shall have included as prior service hereunder all service credited to him or her as creditable service under the terms of one or both of the predecessor systems, provided his or her membership continues unbroken until his or her retirement.

(b) All service of a group A, group C, group D, or group F member since he or she last became a member on account of which contributions are made shall be credited as membership service.

(c) The Retirement Board shall fix and determine by appropriate rules and regulations how much service in any year is equivalent to one year of service, but in no case shall it allow credit for a period of absence without pay of more than a month's duration, except as provided under subsection (e) of this section, nor shall more than one year of service be creditable for all service in one calendar year. Service rendered for the full normal working time in any year shall be equivalent to one year's service, but in no case shall less than 40 calendar weeks be regarded as full normal working time.

(d) Creditable service of a member shall consist of his or her membership service and the prior service, if any, which is credited to him or her under subsection (a) of this section, plus, in the case of a group A member hired prior to July 1, 1978, three years and in the case of a group F member, up to three years of the period served as a State employee prior to 1978 for which the member received no credit provided that the employee served continuously since 1978 until retirement. Creditable service shall also include service as an exempt employee for any period or periods of less than three years prior to 1978, whether or not continuous.

(e) Credit shall also be granted for any period of absence from service certified by the commissioner of the member's department, or if the office of the member is not overseen by a commissioner, then the head of the member's department, due to any class of military service approved by the Retirement Board, provided the employee returns to the service of the State within 90 days after having become discharged or separated from such military service, as if such service had been service as an employee of the State. The earnable compensation of the employee at the time of entering such military service shall be deemed to be the earnable compensation for the period of such service.

(f) Should an employee whose membership is broken again become a member, he or she shall enter the System as a member not entitled to credit for service previously rendered, except as provided in this section or section 463 of this title.

(g) Any member may transfer from a position covered by one group to a position covered by a different group as defined in section 455 of this title and shall be entitled to credit for service rendered in all groups within the System. Benefits shall be based on the accrued value of the credits in the group in which the creditable service was earned and shall be payable according to the provisions of each group, unless the member elects to withdraw his or her contributions in accordance with section 480 of this title. Such benefits shall only be subject to such maximum amounts as are provided for each group and may be combined to exceed 50 percent of average final compensation.

(h) Credit shall also be granted for any period of absence from service in connection with a leave of absence, approved by the commissioner of the member's department, for professional study. If the office of the member is not overseen by a commissioner, then the head of the member's department shall have the authority to approve a leave of absence for professional study. In the case of an approved leave of absence for purposes other than for professional study, service credit shall be granted upon a contribution by the member which equals the member's current contribution rate multiplied by the member's earnable compensation for the year preceding the leave of absence.

(i) Credit shall also be granted for any period of absence from service in connection with an approved workers' compensation claim as a result of a work-related injury, provided the employee provides evidence of the period covered by the approved workers' compensation claim upon return to active service. The earnable compensation of the employee at the time of entering the period of the absence from service resulting from an approved workers' compensation claim or the wages plus all other wage replacement compensation received while on the approved period of absence, whichever provides for the highest total compensation, shall be deemed to be the earnable compensation for the period of service. The total compensation under this subsection shall not exceed what the earnable compensation would have been had the member not been injured. (Added 1971, No. 231 (Adj. Sess.), § 4; amended 1977, No. 153 (Adj. Sess.), § 3; 1981, No. 41, § 5; 1981, No. 108, § 330a; 1985, No. 39, § 1; 1989, No. 78, § 12; 1989, No. 277 (Adj. Sess.), § 17h, eff. Jan. 1, 1991; 1997, No. 68 (Adj. Sess.), § 9, eff. March 1, 1998; 1997, No. 89 (Adj. Sess.), § 4; 1999, No. 158 (Adj. Sess.), § 6; 2001, No. 29, § 1; 2007, No. 13, § 2.)