Q: #412. What do B.C. and A.D. mean?
A: The term B.C. is an abbreviation for “Before Christ,” and the term A.D. in an abbreviation for the Latin words “Anno Domini.” These abbreviations are most closely associated with the Gregorian calendar (named after Pope Gregory XIII), which is the calendar most people use today (although B.C. and A.D. were used prior to this). This calendar was devised in 525 A.D. by a monk named Dionysius Exiguus, who was commissioned create an “Easter table” to determine the day upon which Easter should be celebrated each year. In creating this calendar, Dionysius went back to the birth of Jesus, and decided to make that the dividing point for all of history. Thus, 1 B.C. was before Christ’s birth, 1 A.D. was the year of Christ’s birth (There was no “0,” therefore, it went directly from 1 B.C. to 1 A.D.)
The full Latin term for A.D. is “Anno Domini Nostri Iesu Christi” meaning “In the year of our Lord Jesus Christ.” How Dionysius came up with the year Jesus was born we do not know. However, nearly all scholars agree he was off by a few years, with Jesus instead being born in app. 5-6 B.C. (I explain this more here.) This being the case, B.C. is not technically “Before Christ,” nor is A.D. totally accurate. I should also add here that some believe A.D. stands for “After Death,” but this is obviously not correct since Jesus was “alive” until about 28 or 29 A.D.
The calendar that Dionysius created was not universally accepted until many years later. In 1582, Pope Gregory introduced a slightly revised (more accurate) version of this calendar, and its usage became more common. Prior to this, the Julian calendar, named for and introduced by Julius Caesar in 46 B.C. was the most commonly used calendar. As a result of the revisions made to the Gregorian calendar (by a man named Aloysus Lilius), the length of a year was off by only 26 seconds, as opposed to 11 minutes per year with the Julian calendar. Amazingly, in 1752, to make up for the lost days (and the seasons being out of sync as a result) from using the Julian calendar (11 minutes per year from 46 B.C. to 1752 A.D.) the British calendar was moved forward overnight from September 2nd to September 14th! Can you imagine that?
***Note: It should also be noted that to placate those who do not believe in Christ, the abbreviations B.C. and A.D. are sometimes replaced today with the abbreviations B.C.E. and C.E. meaning “Before Common (or Current) Era” and “Common (or Current) Era.”