Section 12-129. Hours of service during July and August

Four hours on any
  Saturday during the months of July and August, shall constitute  a  full
  day's  work for all employees of any city agency. The head of any agency
  shall have power to employ his or her subordinates on any legal holiday,
  or may employ them on any such Saturday in excess  of  the  legal  day's
  work  above prescribed, paying them compensation therefor at the rate of
  their usual wages or salaries. The  provisions  of  this  section  shall
  apply  to  and  include  per  diem employees, but shall not apply to the
  uniformed forces of the police and fire departments.