<P> Common Era or Current Era (CE) is one of the notation systems for the world's most widely used calendar era--an alternative to the Dionysian AD and BC system . The era preceding CE is known as before the Common Era or before the Current Era (BCE), while the Dionysian era distinguishes eras as AD (anno Domini, "(the) year of (the) Lord") and BC ("before Christ"). Since the two notation systems are numerically equivalent, "2018 CE" corresponds to "AD 2018" and "400 BCE" corresponds to "400 BC". 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 . </P> <P> The expression has been traced back to 1615, when it first appeared in a book by Johannes Kepler as the Latin usage vulgaris aerae, and to 1635 in English as "Vulgar 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 academics . 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 secularism or sensitivity to non-Christians, by not explicitly referencing Jesus as "Christ" and Dominus ("Lord") through use of the abbreviation "AD". </P> <P> 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". </P>

When did we start using ce instead of ad
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