Located in the Eastern (GMT -05:00) time zone. Area code 781 serves the state of Massachusetts. This area code was assigned on June 16th, 1997. On September 1st, 1997 it went into service. 781 is a General Purpose Code. 781 service area does overlap with 339 area codes. Dialing pattern for local calls within the same NPA (area code) is 10D.