A.D.

A.D., abbreviation for anno Domini (Latin, “in the year of our Lord”). The monk Dionysius Exiguus started a system of reckoning years in A.D. 532, using the year in which he believed Christ was born at the beginning of the Christian era. A.D. refers to events that took place after the birth of Christ, and B.C. (before Christ) refers to events that took place before his birth.