The board of trustees may fix and determine by appropriate rules and regulations how much service in any year is equivalent to a year of service but in no case shall more than one year of service be credited in twelve calendar months, nor shall the board allow credit as service for any period of more than one month's duration during which the employee was absent without pay.
HRS § 88-50
Legislature clearly delegated authority to determine the amount of service equivalent to a "year of service" to board of trustees.73 Haw. 9,828 P.2d 260.