A.d. Anno Domini
B.C. Before Christ
As mentioned above, A.D. is the abbreviation for Anno Domini and B.C. is the abbreviation for Before Christ. They are used to label or number the years used with the Julian or Gregorian calendars. The Gregorian calendar is one of the most widely used calendars used in the world today.
There is no Year 0, so the year A.D. 1 immediately follows after the year 1B.C. This dating system was devised in 525, but was not widely used until after the Carolingian Renaissance. The Anno Domini was devised by Dionysius Exiguus to enumerate the years in his Easter Table.
A.D. is the abbreviation for the term Anno Domini which is Latin for 'in the year of our lord'.
B.C. is the abbreviation for the term Before Christ.
A.D. and B.C. are commonly used to count years in time. Jesus Christ's birth is used as the starting point to count years that existed before [B.C.] and after [A.D.] he was born
A.D. Refers to the latin term Anno Domine = In the year of God (or Our Lord) Jesus Chirst.
B. C. refers to the english words Before Christ