M.G.L. c. 149, §§ 48-50

Most employers must allow a worker to have one day off after 6 consecutive days of work. This day off must include an unbroken period between 8 a.m. and 5 p.m.

The laws read:

Chapter 149, Section 48: One day of rest in seven; operation of business on Sunday; violations
Every employer of labor engaged in carrying on any manufacturing, mechanical or mercantile establishment or workshop in the commonwealth shall allow every person, except those specified in section fifty, but including watchmen and employees maintaining fires, employed in such manufacturing, mechanical or mercantile establishment or workshop at least twenty-four consecutive hours of rest, which shall include an unbroken period comprising the hours between eight o'clock in the morning and five o'clock in the evening, in every seven consecutive days. No employer shall operate any such manufacturing, mechanical or mercantile establishment or workshop on Sunday unless he has complied with section fifty-one. Whoever violates this section shall be punished by a fine of three hundred dollars.

Chapter 149, Section 49: Establishments not subject to Sunday work and rest days; railroads or railways
Sections forty-seven and forty-eight shall not apply to establishments used for the manufacture or distribution of gas, electricity, milk or water, to hotels, to the transportation of food, nor to the sale or delivery of food by or in establishments other than restaurants. This section shall not apply to railroads or railways as defined in section one of chapter one hundred and sixty.

Chapter 149, Section 50: Work not subject to Sunday work and rest days
Sections forty-seven and forty-eight shall not apply to (a) janitors; (b) employees whose duties include no work on Sunday other than (1) setting sponges in bakeries, (2) caring for live animals, (3) caring for machinery; (c) employees engaged in the preparation, printing, publication, sale or delivery of newspapers; (d) farm or personal service; (e) any labor called for by an emergency that could not reasonably have been anticipated; (f) pharmacists employed in drug stores.