The Christian era (AD), now used almost exclusively throughout the Western world for civil chronology, was first used in 525 AD by the Christian monk Dionysius Exiguus (c. 500-560 AD), who fixed the birth of Christ in the year of Rome 753. It is generally agreed that this date should have been fixed some years earlier. Dionysius's chronology was introduced into historical writings by Bede the Venerable in the 8th century.
© Copyright Simon & Schuster New Millennium Encyclopedia © 1998 Simon & Schuster, Inc.
* In Roman chronology the era of the founding of the city (ab urbe condita, or AUC) dates from April 22, 753 BC, and the Julian era dates from the reform of the calendar by Julius Caesar in 45 BC., © Copyright Simon & Schuster New Millennium Encyclopedia © 1998 Simon & Schuster, Inc.
** Dionysius Ex•ig•u•us \-eg-©zig-y¡-w¡s\. c.500–c.560. Scythian Christian monk and scholar. In Cyclus Paschalis (525) prepared for Pope St. John I, he introduced method of reckoning the Christian era (Dionysian period) which is still used, making the birth of Christ (incorrectly placed in year 753 of Rome) the starting point of modern chronology. © Copyright Simon & Schuster New Millennium Encyclopedia © 1998 Simon & Schuster, Inc.