On November 14, 2009, permissive 10-digit dialing ends and mandatory 10-digit dialing begins in both area codes 203 and 860. On that day you will be required to dial ten digits in order to call someone within your area code, if your area code is either 203 or 860.
This change is being made in order to facilitate the overlay of area code 475 over area code 203. Even though area code 475 will only be overlaid over area code 203, callers in both area codes 203 and 860 will have to dial all calls with ten digits beginning on November 14th.
Area code 959 is planned as an overlay over area code 860, and has a planned activation date of 2011.
Details at http://nanpa.com/pdf/PL_388.pdf.