Mutual Acceptance is the point when both the buyer and seller agree on the price and terms of a transaction. Both parties are signed around and the agreement has been delivered.
This establishes the timeline for all contingencies and other terms in the agreement. For example, if there is a ten-day inspection period, the ten days would begin the following day (day one) of mutual acceptance date (if it is not a legal holiday).
The computation of time has many characteristics to it that vary depending on weekends, legal holidays what term you are counting, etc. It is important to review the description of how time is computed in the Computation of Time section of the Purchase and Sale agreement.
The careful management of this calendar of events is the job of your agent. As soon as the Purchase and Sale Agreement is signed around and delivered, I create a calendar for my clients, myself and the other agent.