B.C. and A.D. Dates

Open Scroll pages give dates as B.C. and A.D., counted before and after the birth of Christ. This page shows what the letters mean, how to count across the line, and who started counting this way.

Pick a part below.

Part I

What the letters mean

A.D.

Anno Domini

Latin for “in the year of the Lord.” Used for the years counted from the birth of Christ.

B.C.

Before Christ

The years before A.D. 1. Older books also write A.C., for the Latin Ante Christum.

C.E.

Common Era

C.E. stands for Common Era, or Christian Era. The year numbers are the same as A.D.

B.C.E.

Before the Common Era

Also “before the Christian Era.” The year numbers are the same as B.C.

The same years, two sets of letters. 70 C.E. is A.D. 70. 200 B.C.E. is 200 B.C.
You will see both. The Jewish Virtual Library dates the Dead Sea Scrolls from the third century B.C.E. to 68 C.E. That is the third century B.C. to A.D. 68.

Sources: Merriam-Webster, “anno Domini,” “BCE,” “CE,” “Common Era” and “Christian era”; Catholic Encyclopedia (1908), “General Chronology”; Jewish Virtual Library, “The Dead Sea Scrolls.”

Part II

Counting across the line

3 B.C.

2 B.C.

1 B.C.

A.D. 1

A.D. 2

A.D. 3

B.C. years count downA.D. years count up

There is no year 0. The year before A.D. 1 is 1 B.C. The dashed line marks the change.
B.C. years count down. A bigger B.C. number is earlier. 1000 B.C. is before 500 B.C.
Counting across the line, take one off. From 10 B.C. to A.D. 10 is 19 years, not 20, because there is no year 0.

Source: Catholic Encyclopedia (1908), “General Chronology”: “there is no year 0 intervening … between B.C. and A.D.”

Part III

Who started counting this way

About A.D. 527
Dionysius Exiguus, a monk living in Rome, begins counting years from the Incarnation, the coming of Christ. He was also working on the dates of Easter.
His starting point
He placed the Incarnation on 25 March, in the year 754 counted from the founding of the city of Rome.
Later
The Catholic Encyclopedia says many believe Dionysius counted wrong, and that the birth of Christ was three years earlier than he placed it: in the year he would call 3 B.C.

Sources: Catholic Encyclopedia (1909), “Dionysius Exiguus”; Catholic Encyclopedia (1908), “General Chronology.”