The Eras B.c. and A.d

This system of chronology was invented by Dionysius Exigisus about A.D. 532.

It was ordered to be adopted by the bishops assembled at the Council of Chelsea in 816, but it was not generally used until several centuries later.

Charles III. of Germany was the first who added "In the year of our Lord" ("Anno Domini") to his reign (879).

It is now held that Christ was born four years earlier than the era A.D. Christmas, or the festival of Christ's nativity, was first observed in the year A.D. 98.

January 1st of the year A.D. 1 corresponds to the middle of the 149th Olympiad, the 753d year of the building of Rome, Anno Urbis Conditae (A.U.C.), and the year 4714 of the Julian period since the creation.