If the chief of a fire department of a city or town or the chief, chief engineer or head of a fire department of a fire district is on duty at any time on January the first, July the fourth or Christmas day, or the day following when any of said days occurs on Sunday, or the third Monday in February, the third Monday in April, the last Monday in May, the first Monday in September, the second or fourth Monday in October or Thanksgiving day, he shall be granted an additional day's pay.
Massachusetts Legal Code