Every contract has a closing date. If the date comes and goes and the contract doesn't close, you no longer have a contract. You can extend the closing date with a written extension signed by the buyer and seller.
Both parties sign an agreement as to their intentions. Usually BOTH will sign to go forward an give more time.....Time is of the Essence (as the legal term has slways stated) http://www.JeanSOLDMyHouse.com