When closing after October 16 or 17 (for leap year), to receive the full 180 calendar days, you would need to file an extension for your federal tax return of April 15th. For example, if you were to close today, November 4, 2011, without an extension, the last day to complete the exchange would be April 15, 2012 or seventeen days less than the available 180 calendar days. By filing the extension for your tax return, the 180th day is May 2, 2012. 

For over 300 pages of 1031 content, see www.atlas1031.com including explanation of forward and reverse exchanges.