Mass. Gen. Laws ch. 34 § 16
Except as otherwise provided by law, all offices under the jurisdiction of the commissioners shall be open to the public for the transaction of business daily on days other than Saturdays, Sundays and legal holidays for such hours as may be set by the commissioners, except that, if the convenience of the public so requires, the commissioners may keep any office under their jurisdiction open on any Saturday, not a legal holiday, and give any employee required to work on such Saturday equivalent time off without loss of compensation. When the day or the last day for the performance of any act, including the making of any payment or tender of payment, authorized or required to be performed at such an office falls on a Saturday, Sunday or legal holiday, the act may be performed on the next succeeding business day.
Mass. Gen. Laws ch. 34, § 16