B.C. stands for “Before Christ,” as in Jesus Christ. It indicates the number of years before the birth of Jesus (although Jesus himself was born in 4 B.C.). A.D. stands for the Latin phrase Anno Domini. That translates to “In the year of our Lord.” It's used to mark years after the birth of Jesus.

What comes first BC or AD?

BC should appear after the numerical year, while AD should appear before it. BCE and CE should both appear after the numerical year. As is the case with most initialisms, periods may be used after each letter. 1100 B.C., A.D. 1066, 1100 B.C.E., 1066 C.E.

Is BC older than AD?

This calendar era is based on the traditionally reckoned year of the conception or birth of Jesus, with AD counting years from the start of this epoch and BC denoting years before the start of the era. There is no year zero in this scheme; thus the year AD 1 immediately follows the year 1 BC.