180 is the magic number. One hundred and eighty days. If you don’t complete your 1031 Exchange within the IRS mandated time frame, it’s simple. Failed exchange. However there can be exceptions when catastrophic events such as natural disasters occur and only if the IRS issues official notice. If in question, be safe.
Check the IRS’ website. http://www.irs.gov/uac/Tax-Relief-in-Disaster-Situations