(1) The month is the basic period for the awarding of service credit and membership service for all retirement systems.

(a) Except as otherwise specified by rule or statute, 160 hours of service credit will equal one month of service credit, regardless of the calendar period during which the service credit was earned.

(b) Except as otherwise specified by rule or statute, 12 months of service credit will equal one year of service credit, regardless of the calendar period during which the service credit was earned.

(c) Service credit granted for any fiscal year may not be greater than one year.

(2) Service credit of less than 160 hours in a calendar month constitutes part-time service.

(3) If only compensation for full-time covered employment is used to calculate "final average compensation" or "highest average compensation" and if the member has both full- and part-time service, then the member must be granted proportional service credit for service in each calendar month of employment. The proportion will be equal to the number of documented hours for which compensation during a calendar month was reported for the employee, divided by 160 hours, but may not be greater than one.

(4) If only compensation for part-time covered employment is used to calculate "final average compensation" or "highest average compensation" and if the member has both full- and part-time service, then the member must be granted proportional service credit for service in each calendar month of employment. The proportion will be equal to the number of documented hours for which compensation during a calendar month was reported for the employee, divided by the average number of hours worked each month during the "final average compensation" or "highest average compensation" time period, but may not be greater than one.

(5) If compensation for both part-time and full-time covered employment is used to calculate the "final average compensation" or "highest average compensation", then the member must be granted proportional service credit for service in each calendar month of employment. The proportion will be equal to the number of documented hours for which compensation during a calendar month was reported for the employee, divided by the average number of hours worked each month during the "final average compensation" or "highest average compensation" period, but may not be greater than one.