A.D. and B.C. are both abbreviations. A.D. is the abbreviation for anno Domini while B.C. is the abbreviation for before Christ. Both are widely accepted abbreviations that refers to specific calendar years.
Use of A.D.
The abbreviation A.D. for anno Domini means ‘in the year of the Lord’. If you are referring A.D. with a year specified, then you should write A.D. before that figure. For example,
• They ruled in the A.D. 740s.
Use of B.C.
The abbreviation B.C. refers to the years before Christ. Unlike A.D., if you are referring B.C. with a year specified, then you should write B.C. after that figure. For example,
• Some recent research suggests that the dating of Herod’s death might be up for debate and could be dated 1 B.C. (Bill Petro)
- It is assumed to be A.D. or B.C. if there is no reference to any specific year after A.D. or before B.C.
- You cannot write ‘in the fifth century A.D.’ Simply, write ‘in the fifth century’ (without mentioning A.D.).
- However, in the above case, you should mention B.C. (i.e., 21st century B.C.).