The Gregorian calendar is the global standard for the measurement of dates. Despite originating in the Western Christian tradition, its use has spread throughout the world and now transcends religious, cultural and linguistic boundaries. The Gregorian calendar is based on the supposed birth date of Jesus Christ.

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”.

BCE and CE: 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. They have been in frequent use by Jewish academics for more than 100 years, but became more widespread in the later part of the 20th century, replacing BC/AD in a number of fields, notably science and academia.

Religious Neutrality: 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 Since the Gregorian calendar has superseded other calendars to become the international standard, members of non-Christian groups may object to the explicitly Christian origins of BC and AD.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.