Dating of the common era
The first year in Dionysius' Easter table, “Anno Domini 532,” followed the year “Anno Diocletiani 247.” Dionysius made the change specifically to do away with the memory of this emperor who had been a ruthless persecutor of Christians. 1 as the year of Jesus Christ’s birth, but was off in his estimation by a few years, which is why the best modern estimates place Christ’s birth at 4 B. [Related: Easter Science: 6 Facts About Jesus] The addition of the B. component happened two centuries after Dionysius, when the Venerable Bede of Northumbria published his "Ecclesiastical History of the English People" in 731. system to the attention of other scholars, but also expanded the system to include years before A. C.” According to Charles Seife in his book "Zero: The Biography of a Dangerous Idea": “To Bede, also ignorant of the number zero, the year that came before 1 A. Prior years were numbered to count backward to indicate the number of years an event had occurred “before Christ” or “B. For instance, in the date AD 2001, the prefix "AD" stands for "Anno Domini" which is Latin for "the year of our Lord." Similarly, in the date 500 BC, the suffix "BC" stands for "Before Christ." In sixth century Europe, the concept of "zero" was still unknown. Furthermore, modern scholars believe Christ's birth was actually four years earlier than Exiguus thought.
which means Common Era so that they intentionally avoid using the Christian way of dating years.
Perhaps the most unfortunately characteristic of this convention is that "BC" is a suffix (used after the year) while "AD" is a prefix (used before the year).