Ancient and medieval Christian clergy had a dire problem that they needed to solve—the churches of different regions could not decide on how to calculate the date of their holy day of Easter. It was only around 525 A.D./CE, when a monk named Dionysius Exiguus (470-544 A.D./CE) proposed a dating system that could be standardized throughout the various regional churches. He argued that dates after the birth of Jesus should be labeled as Anno Domini, or “In the year of our/the Lord.” Using scripture and other sources he had available to him, Dionysius basically made an educated guess as to where 1 A.D. should be placed on the timeline. Dionysius never claimed that his designation of 1 A.D. was precisely the year that Jesus was born (and the date of Jesus’ birth remains highly debated), but Dionysius kept with his system and started what would become a Western tradition.
Even though Dionysius began the use of A.D. for the years after Jesus’ birth, he did not develop the use of B.C. for the years prior to Jesus—in fact, Dionysius rather wanted to exclude Roman figures like Julius Caesar and Nero from his timeline. It would take another monk with an obsession for finding a standardized date for Easter to bring the use of B.C. into the Western world.
This monk’s name was Bede. He was born near the monastery of Wearmouth in 673 A.D./CE, and spent almost his entire life as a monk. Like Dionysius, he was desperate to unite the different divisions of Christianity under a single system of dating. Bede, sometimes called “the Father of English History,” used Dionysius’ A.D. to designate dates after the birth of Jesus, and began referring to dates that occurred before the birth of Jesus as “B.C.” (Before Christ). Bede’s highly acclaimed achievement, The Ecclesiastical History of the English People (731 A.D./CE), was very influential in spreading the use of B.C. and A.D. in history, both secular and non-secular. By the reign of Charlemagne, the dating style of Dionysius and Bede had become fairly common in Europe, but it would take until the 15th and 16th centuries for the use of A.D. and B.C. to be truly adopted into calendars. Dionysius and Bede’s system of dating remains in use to this day, either as the original B.C. and A.D., or as the more universally used BCE (Before Common Era) and CE (Common Era).
Written by C. Keith Hansley
- From Bede’s Ecclesiastical History of the English People (and relevant letters), translated by Leo Sherley-Pride, R. E. Latham and D. H. Farmer. New York: Penguin Classics, 2003.