christian era

 The era in use in all Christian countries, which was intended to commence with the birth of Christ. The era as now established was first used by Dionysius Exiguus (died about 540), who placed the birth of Christ on the 25th of December in the year of Rome 754, which year he counted as 1 a. d. This date for Christ's birth is now generally thought to be about four years too late.  [Webster 1913 Suppl.]