Mass. Gen. Laws ch. 50, § 4: Computation of time; filing

Section 4. In computing the period of time prescribed in any statute relating to primaries, caucuses or elections, Sundays and holidays shall generally be included; but when the last day of such period falls on a Sunday or on a holiday, the following day shall be considered the final day of such period; and when the first day of such period falls on a Sunday or on a holiday, the day preceding shall be considered the first day of the period. Whenever the day designated for a primary, caucus or election is a holiday, said primary, caucus or election shall be held on the following day.

Except as otherwise provided by section thirty-eight of chapter fifty-three, all certificates of nomination, nomination papers, and other papers pertaining to primaries and elections, required by law to be filed on or before a specified day, shall be filed no later than five o'clock in the afternoon on said day.