N.J. Stat. § 40A:14-48
In cities of the first class, the governing body, by resolution, or the board of fire commissioners or officials in charge of a fire department and force, may divide the members and officers of such fire department and force into 2 platoons, one serving while the other is off duty. Each platoon, respectively, shall alternate the hours of duty for the purpose of alternating the day force with the night force and vice versa, and for the purpose of giving each platoon 24 hours off duty every 6 days. The hours of duty of the day force shall be from 8:00 A.M. to 6:00 P.M. and the night force from 6:00 P.M. to 8:00 A.M. the following morning.
In cases of conflagration or other emergency the officials in charge of the fire department and force shall have authority to retain on duty any or all members and officers of such department and force during the period of the emergency, but in any such case and within 12 months thereafter, such members or officers shall be given a day or proportion thereof off for extra time so served by them during the emergency.
Nothing contained herein shall be deemed to repeal or modify existing laws relating to salaries, annual vacations or sick or disability leaves of the members or officers of such department or force.
N.J.S. § 40A:14-48