Common Era or Current Era (CE) is one of the notation systems for the world's most widely used calendar era. BCE (Before the Common Era/Before the Current Era) is the era before CE. BCE and CE are alternatives to the Dionysian AD and BC system. The Dionysian era distinguishes eras using AD (anno Domini, "[the] year of [the] Lord") and BC ("before Christ"). Since the two notation systems are numerically equivalent, "2019 CE" corresponds to "AD 2019" and "400 BCE" corresponds to "400 BC".[a] Both notations refer to the Gregorian calendar (and its predecessor, the Julian calendar). The year-numbering system utilized by the Gregorian calendar is used throughout the world today, and is an international standard for civil calendars.
The expression has been traced back to 1615, when it first appeared in a book by Johannes Kepler as the Latin usage annus aerae nostrae vulgaris, and to 1635 in English as "Vulgar[b] Era." The term "Common Era" can be found in English as early as 1708, and became more widely used in the mid-19th century by Jewish religious scholars. In the later 20th century, the use of CE and BCE was popularized in academic and scientific publications, and more generally by authors and publishers wishing to emphasize sensitivity to non-Christians, by not explicitly referencing Jesus as "Christ" and Dominus ("Lord") through use of the abbreviation[c] "AD".
The year numbering system used with Common Era notation was devised by the Christian monk Dionysius Exiguus in the year 525 to replace the Era of Martyrs system, because he did not wish to continue the memory of a tyrant who persecuted Christians. He attempted to number years from an initial reference date ("epoch"), an event he referred to as the Incarnation of Jesus. Dionysius labeled the column of the table in which he introduced the new era as "Anni Domini Nostri Jesu Christi".
Numbering years in this manner became more widespread in Europe with its usage by Bede in England in 731. Bede also introduced the practice of dating years before what he supposed was the year of birth of Jesus, and the practice of not using a year zero.[d] In 1422, Portugal became the last Western European country to switch to the system begun by Dionysius.
The term "Common Era" is traced back in English to its appearance as "Vulgar Era" to distinguish dates on the Ecclesiastic calendar in popular use from dates of the regnal year, the year of reign of a sovereign, typically used in national law.
The first use of the Latin term anno aerae nostrae vulgaris[e] discovered so far was in a 1615 book by Johannes Kepler. Kepler uses it again, as ab Anno vulgaris aerae, in a 1616 table of ephemerides, and again, as ab anno vulgaris aerae, 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".
The first so-far-discovered usage of "Christian Era" is as the Latin phrase annus aerae christianae on the title page of a 1584 theology book. In 1649, the Latin phrase annus æræ Christianæ appeared in the title of an English almanac. A 1652 ephemeris is the first instance so-far-found for English usage of "Christian Era".
The English phrase "common Era" appears at least as early as 1708, and in a 1715 book on astronomy is used interchangeably with "Christian Era" and "Vulgar Era". A 1759 history book uses common æra in a generic sense, to refer to the common era of the Jews. The first-so-far found usage of the phrase "before the common era" is in a 1770 work that also uses common era and vulgar era as synonyms, in a translation of a book originally written in German. The 1797 edition of the Encyclopædia Britannica uses the terms vulgar era and common era synonymously. In 1835, in his book Living Oracles, Alexander Campbell, wrote: "The vulgar Era, or Anno Domini; the fourth year of Jesus Christ, the first of which was but eight days", and also refers to the common era as a synonym for vulgar era with "the fact that our Lord was born on the 4th year before the vulgar era, called Anno Domini, thus making (for example) the 42d year from his birth to correspond with the 38th of the common era..." The Catholic Encyclopedia (1909) in at least one article reports all three terms (Christian, Vulgar, Common Era) being commonly understood by the early 20th century.
The phrase "common era", in lower case, also appeared in the 19th century in a generic sense, not necessarily to refer to the Christian Era, but to any system of dates in common use throughout a civilization. Thus, "the common era of the Jews", "the common era of the Mahometans", "common era of the world", "the common era of the foundation of Rome". When it did refer to the Christian Era, it was sometimes qualified, e.g., "common era of the Incarnation", "common era of the Nativity", or "common era of the birth of Christ".
An adapted translation of Common Era into pseudo-Latin as Era Vulgaris (in Latin this means Common Mistress) was adopted in the 20th century by some followers of Aleister Crowley, and thus the abbreviation "e.v." or "EV" may sometimes be seen as a replacement for AD.
History of the use of the CE/BCE abbreviation
Although Jews have their own Hebrew calendar, they often use the Gregorian calendar, without the AD prefix. As early as 1825, the abbreviation VE (for Vulgar Era) was in use among Jews to denote years in the Western calendar. Common Era notation has also been in use for Hebrew lessons for "more than a century".[when?] Some Jewish academics were already using the CE and BCE abbreviations by the mid-19th century, such as in 1856, when Rabbi and historian Morris Jacob Raphall used the abbreviation in his book Post-Biblical History of The Jews.[f]
In general publications, in the 200 years between 1808 and 2008 the ratio of usage of BCE to BC has increased by about 20% and CE to AD by about 50%, primarily since 1980.
More visible uses of Common Era notation have recently surfaced at major museums in the English-speaking world. Furthermore, several style guides now prefer or mandate its usage. Even some style guides for Christian churches prefer its use: for example, the Episcopal Diocese Maryland Church News.
In the United States, the usage of the BCE/CE notation in textbooks is growing. Some publications have moved over to using it exclusively. For example, the 2007 World Almanac was the first edition to switch over to the BCE/CE usage, ending a 138-year usage of the traditional BC/AD dating notation. It is used by the College Board in its history tests, and by the Norton Anthology of English Literature. Others have taken a different approach. The US-based History Channel uses BCE/CE notation in articles on non-Christian religious topics such as Jerusalem and Judaism.
In June 2006, in the United States, the Kentucky State School Board reversed its decision to use BCE and CE in the state's new Program of Studies, leaving education of students about these concepts a matter of discretion at the local level.
Also in 2011, media reports suggested that the BC/AD notation in Australian school textbooks would be replaced by BCE/CE notation. The story became national news and drew opposition from some politicians and church leaders. Weeks after the story broke, the Australian Curriculum, Assessment and Reporting Authority denied the rumour and stated that the BC/AD notation would remain, with CE and BCE as an optional suggested learning activity.
The use of CE in Jewish scholarship was historically motivated by the desire to avoid the implicit "Our Lord" in the abbreviation AD. Although other aspects of dating systems are based in Christian origins, AD is a direct reference to Jesus as Lord.
Proponents of the Common Era notation assert that the use of BCE/CE shows sensitivity to those who use the same year numbering system as the one that originated with and is currently used by Christians, but who are not themselves Christian.
[T]he Christian calendar no longer belongs exclusively to Christians. People of all faiths have taken to using it simply as a matter of convenience. There is so much interaction between people of different faiths and cultures – different civilizations, if you like – that some shared way of reckoning time is a necessity. And so the Christian Era has become the Common Era.
Adena K. Berkowitz, when arguing at the Supreme Court opted to use BCE and CE because "Given the multicultural society that we live in, the traditional Jewish designations – B.C.E. and C.E. – cast a wider net of inclusion". 
Some oppose the Common Era notation for explicitly religious reasons. Because the BC/AD notation is based on the traditional year of the conception or birth of Jesus, some Christians are offended by the removal of the reference to him in era notation. The Southern Baptist Convention supports retaining the BC/AD abbreviations. Roman Catholic priest and writer on interfaith issues Raimon Panikkar argued that the BCE/CE usage is the less inclusive option as, in his view, using the designation BCE/CE is a "return... to the most bigoted Christian colonialism" towards non-Christians, who do not necessarily consider the time period following the beginning of the calendar to be a "common era".
There are also secular concerns. English language expert Kenneth G. Wilson speculated in his style guide that "if we do end by casting aside the AD/BC convention, almost certainly some will argue that we ought to cast aside as well the conventional numbering system [that is, the method of numbering years] itself, given its Christian basis." The short lived French Republican Calendar, for example, began with the first year of the French First Republic and rejected the seven-day week (with its connections to the Book of Genesis) for a ten-day week.
According to a Los Angeles Times report, it was a student's use of BCE/CE notation, inspired by its use within Wikipedia, which prompted the teacher and politician Andrew Schlafly to found Conservapedia, a cultural conservative wiki. One of its "Conservapedia Commandments" is that users must always apply BC/AD notation, since its sponsors perceive BCE/CE notation to "deny the historical basis" of the dating system.
Conventions in style guides
The abbreviation BCE, just as with BC, always follows the year number. Unlike AD, which traditionally precedes the year number, CE always follows the year number (if context requires that it be written at all). Thus, the current year is written as 2019 in both notations (or, if further clarity is needed, as 2019 CE, or as AD 2019), and the year that Socrates died is represented as 399 BCE (the same year that is represented by 399 BC in the BC/AD notation). The abbreviations are sometimes written with small capital letters, or with periods (e.g., "B.C.E." or "C.E."). Style guides for academic texts on religion generally prefer BCE/CE to BC/AD.
Similar conventions in other languages
- In Germany, Jews in Berlin seem to have already been using "(Before the) Common Era" in the 18th century, while others like Moses Mendelssohn opposed this usage as it would hinder the integration of Jews into German society. The formulation seems to have persisted among German Jews in the 19th century in forms like vor der gewöhnlichen Zeitrechnung (before the common chronology).
- In 1938 Nazi Germany, the use of this convention was also prescribed by the National Socialist Teachers League. 
- However, it was soon discovered that many German Jews had been using the convention ever since the 18th century, and they found it ironic to see " Aryans following Jewish example nearly 200 years later". 
- In Spanish, common forms used for "BC" are aC and a. de C. (for "antes de Cristo", "before Christ"), with variations in punctuation and sometimes the use of J.C. (Jesucristo) instead of C. In scholarly writing, AEC is the equivalent of the English "BCE", "antes de la Era Común" or "Before the Common Era".
- In Welsh, OC can be expanded to equivalents of both AD (Oed Crist) and CE (Oes Cyffredin); for dates before the Common Era, CC (traditionally, Cyn Crist) is used exclusively, as Cyn yr Oes Cyffredin would abbreviate to a mild obscenity.
- Беларуская (тарашкевіца)
- Lingua Franca Nova
- La .lojban.
- Norsk nynorsk
- Simple English
- Srpskohrvatski / српскохрватски
- Tiếng Việt