Dates BC and AD

The idea to count years from the birth of Jesus Christ was first proposed in the year 525 by Dionysius Exiguus, a Christian monk. Standardized under the Julian and Gregorian calendars, the system spread throughout Europe and the Christian world during the centuries that followed. AD stands for Anno Domini, Latin for "in the year of the Lord", while BC stands for "before Christ".

CE stands for "common (or current) era", while BCE stands for "before the common (or current) era". These abbreviations have a shorter history than BC and AD, although they still date from at least the early 1700s.

An important reason for adopting BCE/CE is religious neutrality. Since the Gregorian calendar has superseded other calendars to become the international standard, members of non-Christian groups may object to the explicitly Christian origins of BC and AD. Particularly problematic is AD ("in the year of the Lord"), and its unavoidable implication that the Lord in question is Jesus Christ.

Religious neutrality was the main rationale behind Jewish academics adoption of BCE/CE over a century ago, and continues to be its most widely cited justification. However, others object to the BC/AD system on the basis that it is objectively inaccurate. It is widely accepted that the actual birth of Jesus occurred at least two years before AD 1, and so some argue that explicitly linking years to an erroneous birthdate for Jesus is arbitrary or even misleading. BCE/CE avoids this inaccuracy since it does not explicitly refer to the birth of Jesus, removing some of the baggage associated with our dating system while also acknowledging that the starting point for 1 CE is essentially a convention.