Why don't you use the abbreviation AD anymore?

The abbreviation AD stands for Anno Domini, which is Latin for Year of the Lord. Dates given in this format are counted from the year once considered to be the year of the birth of Jesus ("the Lord").

A date system which refers to Jesus is not appropriate for the many religions other than Christianity. However, since this system of dating is in such widespread use throughout the world and is the standard system internationally, agreeing and adopting a new system would have been a lengthy process. The system has been kept but the terminology has been changed.

AD (Anno Domini) is now CE (Common Era)

BC (Before Christ) is now BCE (Before Common Era).