Common Era (also Current Era or Christian Era), abbreviated as CE, is an alternative naming of the traditional calendar era, Anno Domini (abbreviated AD). BCE is the abbreviation for Before the Common/Current/Christian Era (an alternative to Before Christ, abbreviated BC). The CE/BCE designation uses the year-numbering system introduced by the 6th-century Christian monk Dionysius Exiguus, who started the Anno Domini designation, intending the beginning of the life of Jesus to be the reference date. Neither notation includes a year zero,and the two notations (CE/BCE and AD/BC) are numerically equivalent; thus “2014 CE” corresponds to “AD 2014”, and “399 BCE” corresponds to “399 BC”. The expression “Common Era” can be found as early as 1708 in English,and traced back to Latin usage among European Christians to 1615, as vulgaris aerae,and to 1635 in English as Vulgar Era. At those times, the expressions were all used interchangeably with “Christian Era”, with “vulgar” meaning “ordinary, common, or not regal” rather than “crudely indecent”. Use of the CE abbreviation was introduced by Jewish academics in the mid-19th century. Since the later 20th century, use of CE and BCE has been popularized in academic and scientific publications, and more generally by publishers emphasizing secularism or sensitivity to non-Christians. The Gregorian calendar and the year-numbering system associated with it is the calendar system with most widespread use in the world today. For decades, it has been the global standard, recognized by international institutions such as the United Nations and the Universal Postal Union. The CE/BCE notation has been adopted by some authors and publishers wishing to be neutral or sensitive to non-Christians because it does not explicitly make use of religious titles for Jesus, such as “Christ” and Domin- (“Lord”), which are used in the BC/AD notation, nor does it give implicit expression to the Christian creed that Jesus was the Christ. Among the reasons given by those who oppose the use of Common Era notation is that it is selective as other aspects of the Western calendar have origins in various belief systems (e.g., January is named for Janus), and claims that its propagation is the result of secularization, anti-supernaturalism, religious pluralism, and political correctness.
The term “Common Era” is traced back in English to its appearance as “Vulgar Era” to distinguish it from the regnal dating systems typically used in national law. The first use of the Latin equivalent (vulgaris aerae) discovered so far was in a 1615 book by Johannes Kepler.Kepler uses it again in a 1616 table of ephemerides, and again in 1617. A 1635 English edition of that book has the title page in English – so far, the earliest-found usage of Vulgar Era in English. A 1701 book edited by John LeClerc includes “Before Christ according to the Vulgar Æra, 6”. A 1716 book in English by Dean Humphrey Prideaux says, “before the beginning of the vulgar æra, by which we now compute the years from his incarnation.” A 1796 book uses the term “vulgar era of the nativity”.