A Practice Note explaining how to compute time periods in Massachusetts civil litigation. Specifically, this Note explains how to compute time periods under Massachusetts Rule of Civil Procedure 6 and state law, identify triggering events, calculate forward-looking and backward-looking deadlines, and determine the waiting period for motions served under Massachusetts Superior Court Rule 9A. This Note also explains how to account for automatic extensions when additional days are added to time periods, including weekends, legal holidays, service-based extensions for mail and electronically filed notices and documents, and extensions because of public emergencies.