BackgroundDionysius Exiguus, later known as Dennis the Humble, was born in in the Roman empire around the year A.D. 470. Little is known about his life, but most believe he was born in the section of the Roman Empire known as Scythia Minor. He was amember of the Scythian monks from the city of Tomis. Dionysius was a Catholic and was fluent in both Latin and Greek.
The main work of Dionysius was a Scythian monk was to translate religious documents from Greek to Latin. His translated works include The Life of St. Pachomius and Instruction of St. Proclus of Constantinople. He also translated a history of the discovery of the head of St. John the Baptist. In total, Dionysius is said to have translated 401 ecclesiastical canons which were collected into the book Collectio Dionysiana. At the request of Pope John I in 525, Dionysius also created a table listing out all the future dates of Easter and a set of arguments justifying the calculations. Dionysius ignored the Easter Tables used by the Church of Rome that were prepared in 457 by Victorius of Aquitaine. He stated that they did not obey Alexandrian principles. His tables were not, however, used to calculate Easter, using, instead, the tables created by Cyril of Alexandria. By far, though, Dionysius 's most famous work is as the inventor of the Anno Domini era. Using different references and documents, Dionysius calculated the year in which Jesus was born, stating that the year that he made this calculation was 525 years "since the incarnation of our Lord Jesus Christ." This year system was then applied to both the Julian and the Gregorian calender as a way of referencing the year. Before the birth of Jesus, the years are noted as B.C., or the years Before Christ. The years after the birth of Jesus are noted with A.D., or Anno Domini, or "In the Year of Our Lord. The Anno Domini era became dominant in Western Europe after it was used in 731 by the Venerable Bede to date events in his book, Ecclesiastical History of the English People. The Anno Domini year system is now the most used system of noting the year.
Not much is known about the death of Dionysius Exiguus except that it was around the year A.D. 544. Dionysius is on our list because without him, we would really have a way of telling what year he did die in. Even though some people now use the notation C.E. and B.C.E. (Current Era and Before Current Era), they still are based on Dionysius's calculation of the birth of Jesus, and even though Dionysius's calculation are off by about three years, his system was still accepted and is used to this day. Without him, we wouldn't have any cool doomsday names like "Y2K" or "Twenty-Twelve."