The initials B.C. (an abbreviation for “Before Christ”) are applied to dates of events that occurred before the “Christian” (or Common) era. If the information Luke gives in his Gospel can be used as a guide (Luke 1:5; 2:1), then Jesus was born at least four years before the years known as A.D. began. (A.D. is an abbreviation of the Latin phrase anno domini, meaning “in the year of our Lord.”) Numbering years based on the year of Jesus’ birth was actually not used until A.D. 526 when the system was introduced by a monk named Dionysius Exiguus. He was given the job of creating a calendar for the feasts of the church. He fixed the birth of Jesus in the Roman year 754, which was selected as the first year of the Christian era beginning on January 1. Dionysius apparently misjudged Herod’s reign by about five years. However, by the time his error was discovered, his system had already been widely adopted by church and civil authorities.

The initials B.C.E. (Before the Common Era) and C.E. (in the Common Era) are sometimes used for the more traditional B.C. and A.D.