The term BC is short for "Before Christ." and AD for ?
Historical dates before the birth of Christ become smaller as they approach the theoretical but non-existent Year Zero.
The term AD is short for "Anno Domini" (Latin "year of our Lord").
Historical dates after the birth of Christ are classified as AD. (Contrary to popular belief, AD does not stand for After Death.) The BC/AD system for identifying historical dates has been in continuous use since the earliest part of the Middle Ages, along with the separate Hebrew and Islamic (Hijri) calendar years.
