The board shall determine, by appropriate rules and regulations, how much service in any year is the equivalent of a year of service, but in no case shall it allow credit for more than one (1) year of service for all service rendered in any period of twelve (12) consecutive months. With respect to legislative officials elected by the general assembly or appointed by the speakers thereof and thereafter elected by the general assembly as elected officials, their years of service shall be deemed to be both years of the general assembly which elected them or for which they were appointed.
T.C.A. § 8-3415