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.
first used "Vulgar Era" to distinguish dates on the Christian calendar from the regnal year
typically used in national law.
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". 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.