Mass. Gen. Laws ch. 4 § 10
At two o'clock ante-meridian of the last Sunday in April of each year, the standard time in this commonwealth shall be advanced one hour, and at two o'clock ante-meridian of the last Sunday in October of each year the standard time in this commonwealth shall, by the retarding of one hour, be made to coincide with the mean astronomical time of the degree of longitude governing the zone wherein the commonwealth is situated, the standard official time of which is described as United States standard eastern time, so that between the last Sunday of April at two o'clock ante-meridian and the last Sunday in October at two o'clock ante-meridian in each year the standard time in this commonwealth shall be one hour in advance of the United States standard eastern time. And in all laws, statutes, orders, decrees, rules and regulations relating to the time of performance of any act by any officer or department of the commonwealth, or of any county, city, town or district thereof, or relating to the time in which any rights shall accrue or determine, or within which any act shall or shall not be performed by any person subject to the jurisdiction of the commonwealth, and in all the public schools and in all institutions of the commonwealth, or of any county, city, town or district thereof, and in all contracts or choses in action made or to be performed in the commonwealth, it shall be understood and intended that the time shall be United States standard eastern time as changed by this section.
Mass. Gen. Laws ch. 4, § 10