N.J. Stat. Ann. § 40A:14-52

In any municipality, the governing body, by ordinance, may adopt a schedule of hours of actual duty for the paid officers and members of the fire department and force, to average for each 42 hours per week in any 8-week cycle, except in cases of emergency the official in charge shall have authority to retain on duty any member or officer during the emergency, but in any such case and within 12 months thereafter such member or officer shall be given compensatory time off for all hours worked in excess of the said average, so served by him during the emergency.