The
Common Era refers to the conventional
Gregorian numbering of years from an
epoch based on the traditionally reckoned year of the birth of
Jesus Christ.
This convention for year numbering was introduced by
Christians in the
6th century, although it was not widely used until later.
Years before the epoch were denoted
A.C.N.
(for
Ante Christi Natus,
Latin for "before the birth of Christ"),
although
B.C. ("Before Christ") is now usually used in
English.
These abbreviations are placed after the year number, which is counted backward from 1; that is,
the first year before the epoch is "1 B.C.", the second year before the epoch is "2 B.C.", etc.
Years after the epoch are denoted
A.D.
(for
Anno Domini, Latin for "in the year of the Lord"), with the abbreviation before the year
and counted from 1. So the first year of the epoch is "A.D. 1" (there being no year 0), etc.
C.E., an abbreviation for "Common Era" or "Christian Era", is equivalent to A.D., but is placed after
the year, and is preferred by some in secular writing.
B.C.E., an abbreviation for "Before Common Era" or "Before Christian Era", is equivalent to B.C., and is likewise placed after the year number.
Due to the dominant influence of Christianity in the development of Western civilization over the last 2,000 years, the initials B.C. (or A.C.N) and A.D. have been used without question for many centuries.
Rejecting the historical domination of Christianity over Western civilization, the movement to substitute B.C.E./C.E. for B.C./A.D. has grown along with political correctness in Western academia.
See also Anno Domini.