The abbreviation A.D. is short for "Anni Domini Nostri Jesu Christi", i.e., "in the year of Our Lord Jesus Christ". Since Muslims, Jews, etc., may not be entirely comfortable with this, the designation "A.D." is now sometimes replaced by the more neutral C.E. (for "Christian Era"), and instead of B.C. ("Before Christ") B.C.E. (for "Before Christian Era") is sometimes used.

CE is also an abbreviation of "Common Era". The Common Era Calendar is the same as the Gregorian Calendar except that instead of numbering years BC/AD the astronomical system of year numbering is used (this system is explained in the next section). In this article (and elsewhere on this website) dates designated "CE" are almost always dates in this Common Era Calendar. Note that "BCE" is not used with dates in the Common Era Calendar. The date 2 BCE, meaning the year 2 "before Christian Era", a.k.a. 2 BC, is the same as the year -1 CE.

http://www.hermetic.ch/cal_stud/cal_art.html#Adoption