This is a common scenario in home sales. This is a question that you should direct to your attorney, because they routinely deal with scheduling closing dates for real estate transactions. If you are buying a home in New Jersey, and do not have an attorney, that is a mistake, because there numerous questions and issues that need to be dealt with; as well as misconceptions about the process such as the one in your question. Typically, the closing date in a real estate contract is a "target" date, not a firm date. You can usually reschedule it, or delay it, and it does not void the contract. There are other repercussions, usually that the buyer can demand a closing be set for a firm date afterwards, but you really need to speak with your attorney to understand the process. A two week delay is more common that not.
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Generally speaking, no that will not void the contract unless a Time is of the essence letter was sent. Since I do not know what is in the file, I cannot give you a definitive answer. You should contact your attorney and ask, since he is familiar with the file
Whether you can push back the closing date will be dictated by the terms of your contract. If the contract states that the dates for performance are "of the essence", then you may be liable to the buyer for any costs they incur due to the delay. If the closing date was not made "of the essence", then you can push it back without penalty. If the contract does not make the closing of the essence, then the buyer's would have to send a written demand to close and setting a specific date as the of the essence date - which is typically 10 or more days after the letter is recieved.
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