Why did they count down in BC?

“B.C.” stands for “before Christ.” The system labels years based on a traditional notion of when Jesus was born — with the “A.D.” denoting years after his birth and “B.C.” designating the years that predate his birth. In English, it is common for “A.D.” to precede the year, so that the translation of “A.D.

Do BC dates count down?

B.C. (or BC) – meaning “Before Christ”. Used for years before AD 1, counting backwards so the year n BC is n years before AD 1. Thus there is no year 0.