(1) "Service" means service rendered to this state by an elected or appointed state official or employee of this state. Credit for service shall be determined by appropriate rules and regulations of the retirement board, but not more than 1 year of service shall be creditable for all service in 1 calendar year. The retirement board shall not allow credit for service for any period of more than 1 month in any 1 calendar year during which the employee was absent without pay. However, full service credit shall be given for a period during which an employee is on leave of absence and is receiving worker's compensation benefits as the result of a duty-incurred disability. Full service credit shall also be given to an employee for required 1-day layoffs, for voluntary or involuntary participation in pay reduction plan A, pay reduction plan B, or both, in effect during the fiscal years ending on and after September 30, 1981, for required and designated temporary layoffs, and, beginning October 1, 2003, for furlough hours, and for participation in the banked leave time program.

    (2) "State treasurer" means the treasurer of this state.

    (3) "Tier 1" means the retirement plan available to a member under this act who was first employed and entered upon the payroll before March 31, 1997 and who does not elect to become a qualified participant of Tier 2.

    (4) "Tier 2" means the retirement plan established pursuant to section 401(k) of the internal revenue code that is available to qualified participants under sections 50 to 69.