A.D. means "Anno Domini" or "In the Year of Our Lord" as in "On the 14th of May in the Year of Our Lord 1607 the Jamestown Colony was established."
B.C., meaning (years) Before Christ, comes after the date, as in "Cleopatra reigned in Egypt from 51 to 30 B.C."
If you're using B.C.E. and C.E., (Before Common Era and Common Era), those both come after the date.
As usual, Wikipedia has more complete poop.