Mass. Gen. Laws ch. 51, § 28

Registrars shall hold a continuous session from 9:00 a.m. until 5:00 p.m. on the last day for registration established under section 26; provided, however, that a town having less than 1,500 voters may hold a session from 9:00 a.m. until 11:00 a.m. and from 3:00 p.m. until 5:00 p.m.