A.D. is “Anno Domini” which means “In the year of our Lord” and refers to the year Christ was born.

AD as previously stated stands for Anno Domini, Latin for The Year of our Lord.

Anno Domini (Latin : “In the year of (Our) Lord”[1]), abbreviated as AD or A.D., defines an epoch based on the traditionally reckoned year of the conception or birth of Jesus of Nazareth. AD is also an abbreviation for Christian Era.[2] Similarly, Before Christ (from the Ancient Greek “Christos” or “Anointed One”, referring to Jesus), abbreviated as BC or B.C., is used in the English language to denote years before the start of this epoch. Some prefer the alternatives ‘CE’ and ‘BCE’, arguing that they are more neutral terms

AD-Anno Dominie, literally ‘in the year of Our Lord’ (years calculated from the birth of Christ): 0 + AD. Now called CE-Christian Era.

There are no years between.