Origins of the Terms BC and AD


The credit for the terms BC and AD for the Christian calendar belong to the Scythian monk Dionysius Exiguus who lived in the middle of the 6th century. However, this is only halfway accurate.

First of all, Dionysius’ scholarly concerns were all wrapped around a desire to establish a correct date for Easter. The question of when exactly the Resurrection should be commemorated was one of the chief concerns of theologians at this time (the Middle Ages). But in all of his exploring of dates and calendars, he became increasingly dissatisfied with the common designation for years as being “AD” meaning “after Diocletian.” Diocletian was a Roman emperor who had instigated a major persecution of Christians during his rule. Dionysius thought it was wrong that Christians should use a calendar honoring a man who had tried to eradicate Christianity.  So Dionysius decided to leave the “AD” abbreviation but have them signify the years following Christ’s birth instead, and also to assign them new meaning. He designated AD to stand for the Latin phrase “Anno Domini,” meaning “in the year of the Lord,” So the AD remained, but it’s meaning was now centered on Christ. Then he chose AC, “Ante Christum,” Latin for “before Christ,”  for the years preceding Christ. Obviously, that designation did not stick.

Dating the Year of Christ’s Birth

Dionysius also began trying to calculate the date for the birth of Christ. He placed this date on the eighth day before the Calends of January in the year 753 “ab urbe conditâ,” that is, “after the founding of Rome.” Eight days later became the first day of the year, January 1 of the year AD 1. So, Dionysius set Jesus’ birth just before AD 1. That means Jesus was born in the year “0,” right? Wrong. Dionysius appointed that year to be 1 BC (really AC to him–remember?). Thus, his calendar (and ours today) leaped from 1 BC to 1 AD. There is no year zero. This makes for some interesting math when you calculate time periods that span across the BC-AD bridge, and it usually involves adding or subtracting one year to make up for the missing 0 (a definite annoyance to history teachers and students alike). But Dionysius really had no choice because zero was not yet invented in Europe yet. India had it, and also the Mayans in American, but it was almost another 1000 years before Europeans devised its use in math. 

Thus, Dionysius gave us the term AD for Anno Domini, and he gave us the designation for the year 1 on our calendar based on his calculations for Jesus’ birth.

So what about BC?

The term BC comes from Saint Bede, an English monk, who in 731 AD used it in some of his writings. Bede simply went with the English language designation of “Before Christ.” Because of Bede’s high ranking as a scholar (he is known as the Father of English History), his designation stuck.

Thus, we ended up with AD standing for a Latin phrase and BC standing for one in English. Just to confuse students, I suppose.

New Modern Terms

The majority of scholars today no longer use the terms BC or AD, instead the terms BCE and CE have taken over from the traditional terms.  BCE stands for “Before the Common Era,” and, of course, CE is simply “Common Era.” Dionysius and Bede would be disappointed that modern secular historians have rejected the tradition of dating the calendar around the coming of the Christ. But still, if you ask any historian why the dates shift from BCE to CE at that particular point in history, he or she would have to admit that the only answer is that it is the traditional date for the birth of Jesus Christ, the founder of Christianity. So, they can call it by the new initials, but like it or not, His birth is still the pivot upon which our history turns. They can’t change that.


And One Last Note: Although Dionysius did a scholarly job for his day and age, he did get things a little bit wrong. Herod the Great, who greeted the wise men as they came through Jerusalem and who slaughtered the babies in Bethlehem, died in April of 4 BC. So most scholars agree that Jesus must have been born before that time.