Is there a breach of contract if the sell of the home does not take place on the original closing date? I''m selling my home on a short sale contract.

The answer to your question depends on the terms of your contract.  In the jurisdictions in which I practice (warning - I don't practice in Virginia) the closing date listed in the contract is not binding unless it has been made "of the essence".  Closings are often adjourned until one side or the other notifies the other that the closing date is firm and "time is of the essence".  At that point, the closing date is set and cannot be changed with impunity, although sometimes valid excuses come up.  Sometimes time is made of the essence in the original contract, and that may well be how your contract reads, given that you are engaged in a short sale.