New York Codes, Rules and Regulations
Title 2 - DEPARTMENT OF AUDIT AND CONTROL
Chapter VI - New York State and Local Employees' Retirement System and New York State and Local Police and Fire Retirement System
Part 370 - Service Credit For Tier 1 Members Of The New York State And Local Retirement Systems
Section 370.3 - Positions for which service credit will be prorated for less than full-time service

(a) Employees paid on an hourly, daily or per meeting employment. With respect to individuals employed on an hourly or per diem basis, the service shall be credited based on the fraction determined by dividing the number of hours/days worked in a month to the number of hours/days that is considered full-time for the position. An individual who is paid on a per meeting basis shall be considered to be employed on a per diem basis, and a meeting attended by such individual shall be considered a day of work for service crediting purposes.

(b) Positions in which the member is employed to work a percentage of a full-time position. Service credit shall be based on the percentage of time the individual is employed to work. For example, if an individual is hired to work 50 percent of a full-time position, the individual will receive one-half of a year's credit for paid service on the payroll for an entire year.