N.J. Stat. Ann. § 40A:14-133

The days of employment of any member or officer of the police department or force, including any officer having supervision or regulation of traffic upon county roads, parks and parkways shall not exceed 6 days in any one week, except in cases of emergency the officer, board or official in charge of such police department or force shall have authority to retain on duty any member or officer during the period of the emergency, but in any such case and within 12 months thereafter, such member or officer shall be given a day off for each extra day so served by him during the emergency.