Section 13-349. Retirement; minimum period for service retirement

Any member
  in  city-service  who  shall  have attained the minimum age or period of
  service retirement elected by him or her upon his  or  her  own  written
  application  to and filed with the board setting forth at what time, not
  less than thirty days subsequent to the execution and filing thereof, he
  or she desires to be retired, shall be retired as of the date  specified
  in  said  application, provided that at the time so specified for his or
  her retirement, his or her term or tenure of office or employment  shall
  not  have  terminated or have been forfeited, provided further that upon
  his or her request in writing the member shall be  granted  a  leave  of
  absence  from  the  date  of  filing said application until the date the
  retirement becomes effective.