Mass. Gen. Laws ch. 48 § 59
The permanent members of the uniformed fire fighting force in every town which accepts this section or has accepted corresponding provisions of earlier laws shall be divided by the fire commissioner, board of fire commissioners, chief engineer, board of engineers, or other officers having charge of the fire fighting force into two bodies or platoons, which shall be designated as a day force and a night force, and shall alternate on tours of duty every third day.
The hours of duty of the day force shall be from eight o'clock in the forenoon to six o'clock in the afternoon, and the hours of duty of the night force shall be from six o'clock in the afternoon to eight o'clock in the forenoon; provided, that on every third day, for the purpose of alternating the day force with the night force and vice versa, the number of hours of duty herein stated may be exceeded, but one force shall be at liberty at all times, except that in case of a conflagration the officer or board having charge of the fire fighting force shall have full authority to summon and keep on duty all members of the fire fighting force while the conflagration continues.
This section shall not affect any law, ordinance or by-law relative to salary, pensions, annual vacations or sick or disability leave of absence of the members of the fire fighting force in any town subject to this section. Sections fifty-six and fifty-seven shall not apply to the permanent members of the uniformed fire fighting force in any such town.
All ordinances or by-laws, or parts thereof, affecting the number that may be appointed as members of a fire fighting force, or the meal hours or days off of the members of the fire department of any such town, shall have no force after its acceptance becomes effective.
Upon petition of not less than ten per cent of the registered voters in any town, duly certified by the registrars of voters and filed with the town clerk not less than sixty days before any annual town meeting, the town clerk shall cause to be printed upon the official ballot used for the election of town officers at such annual town meeting the following question: "Shall section fifty-nine of chapter forty-eight of the General Laws, providing for the division into day and night forces of permanent members of fire departments, known as the two platoon system, be accepted?" If a majority of the votes cast on the said question in any town are in the affirmative, this section shall take effect in such town ninety days thereafter.
Mass. Gen. Laws ch. 48, § 59