What do BC and AD actually mean?
The two letters on nearly every date you write are a piece of theology in disguise: the world's calendar counts its years from the birth of one Child in Bethlehem. That raises two questions worth asking — what do the abbreviations actually say, and why did history end up being measured from that point at all?
What the Letters Say
One writer states the plain meaning of both abbreviations, and notes how far their use reaches — into private letters, business, and the laws of nations.
A. J. PollockIt was His birth in the humble stable of the inn at Bethlehem that has divided time into two parts in the reckoning of the civilised nations of the world. For hundreds of years, day after day, millions upon millions have dated their letters, business men their correspondence, parliaments their statutes, as so many years since our Lord was born. The letters B.C. stand for Before Christ; the letters A.D. (Anno Domini, Latin, in the year of our Lord), stand for After Christ. This surely testifies to the very deep and profound impression that our Lord, crucified in shame and disgrace after only a very brief three-and-a-half years of public service, made on mankind.
So B.C. is English — "Before Christ." A.D. is Latin — Anno Domini, "in the year of our Lord." It is a statement about whose years these are, not merely a count of years after an event.
Why History Splits There
The division is not an accident of bookkeeping. Commentators see the coming of Christ as the true hinge of all human history, with everything before and after facing toward Him.
Samuel RidoutThe "times past" refer to the old dispensation, all that took place up to the coming of Christ. It is Christ who divides all history. Everything before pointed toward Him; and everything since points back to Christ, or, rather, I might say, points up to Him. Christ is the great Centre, the only centre of God's thoughts; the centre of all there is in creation, in the history of man, and in all that the heart can conceive.
The same thought is put in terms of direction and movement — the whole run of the ages was heading somewhere.
James McBroomChrist stands before us in the Gospels as the ultimate end towards which all time, all nature, all history hastened. The whole march of events down through the ages, with every movement of divine testimony in the progress of revelation, had Him as their goal.
A Witness Signed by Everyone
The striking thing about A.D. is who uses it. People who reject the claims of Christ still date their documents by Him.
A. J. PollockWe write under date of 1930 — that is 1930 years since Christ appeared. Is it not astounding that every day Christians and unbelievers, Jews and Turks, Roman Catholics and Protestants, should all date their letters and business correspondence by the appearing of (as the world would say) an obscure carpenter's son in an obscure village in an obscure country?
The Numbering Is Slightly Off
Our era was fixed by a calculation made centuries after the event, and commentators agree the sum was not exact. Working from the date of Herod's death, one writer traces the mistake and shows that scholars land on different corrections.
William KellyDionysius the Little, at the beginning of the sixth century, reckoned the year of the Birth as 753, after the founding of Rome; but it is certain that Herod died, as stated above, in 750. So three or four years have to be deducted from 753; and so 749, that is, 4 "B.C.," as Ellicott; while 5 "B.C." is taken as the date by Godet for the fifteenth year of Tiberius. Kepler, however, who has been followed by Alford, calculated that the Nativity took place in 6 "B.C."
Commentators differ on the precise figure, but the general correction is widely shared: most chronologists put the birth "at least four years earlier than our common era, A.D." (The Bible Treasury). Christ was, oddly enough, born a few years "before Christ."
The Year of the Lord Still Running
There is a second sense in which we live in "the year of the Lord" — a stretch of time held open on purpose.
A. J. PollockNote the acceptable year of the LORD, the long stretched-out 365 days of gracious waiting on man for his blessing, as compared with "the day of vengeance of our God," the short sharp 24 hours in which judgment shall be rendered to every man. "The acceptable year of our Lord" has already lasted nearly two thousand years, and still God lingers in grace over a godless world.
Summary
- Meaning. B.C. is "Before Christ"; A.D. is Anno Domini, Latin for "in the year of our Lord" — the calendar names an owner, not just a starting point.
- Centre. Time splits there because Christ splits history: everything before pointed toward Him, everything since points back up to Him.
- Reach. The claim runs through private letters, business papers, and the statutes of parliaments — believers and unbelievers alike sign it daily.
- Accuracy. The sixth-century calculation was a few years out; commentators differ between 4, 5 and 6 B.C. for the actual birth.
- Result. The years still labelled "of our Lord" are the acceptable year — patient, stretched-out grace, before the short, sharp day of vengeance.