Year 666 (DCLXVI) was a common year starting on Thursday (link will display the full calendar) of the Julian calendar. The denomination 666 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.
By place 
Europe Chertsey Abbey is founded.Barking Abbey is founded.Wilfrid returns from France newly consecrated as Bishop of York.
China Chinese Buddhist monks Zhi Yu and Zhi You craft more South Pointing Chariot vehicles for Emperor Tenji of Japan, as recorded in the Nihon Shoki (the South Pointing Chariot is a non-magnetic, mechanical-driven directional-compass vehicle that incorporates the use of a differential gear).