A.D.

In the year of our Lord. The A.D. should precede the date and never be used with in, since that would be superfluous. Nor should the A.D. be used when speaking of a century.

   Wrong: He died in 1865 A.D.
   Right: He died A.D. 1865.
   Wrong: We live in the 20th century A.D.
   Right: We live in the 20th century of the Christian Era.

From the American College Encyclopedic Dictionary, vol. II (1952)

In some countries' postal systems, a delivery report can be requested.

This is commonly referred to as "Acknowledgement Due" request, and letters sent thus are captioned with an "A.D" or a "Registered A.D."