Dionysius the "Little" (the English translation of Exiguus), a name he evidently took on himself as a self-deprecating tag, and not having anything to do with his height.
Dionysius Exiguus was known for:
Inventing the Christian calendar.
Places of Residence and Influence:
Hired to create a Christian chronology by Pope John I: 525
About Dionysius Exiguus:
Dionysius was born sometime in the late fifth century, probably around 470 or so, most likely in Scythia, where he became a monk. In the 490s, he was summoned to Rome by Pope Gelasius in order to systematize the pontifical archives. It may have been around this time that he met the historian Cassiodorus, who became his friend and would later write about Dionysius and his achievements.
When Gelasius died in 496, Dionysius stayed on in Rome to continue his education. Not only did he become proficient in theology, Scripture, and canon law, but he was also well-regarded as a mathematician and astronomer. He is credited with writing over 400 ecclesiastical canons, and he evidently recorded the decrees of the Council of Nicaea, the Council of Constantinople, the Council of Chalcedon and the Council of Sardis. Dionysius also translated many works from Greek to Latin, though these are now lost. While working to improve his knowledge, Dionysius eventually became abbot of a monastery in Rome.
In 525, Pope John I asked Dionysius to prepare a Christian chronology. Using tables evolved by Theophilus of Alexandria, Dionysius set the birth of Jesus according to the Roman system of daing at 753 years after the founding of the Eternal City. This, as it turned out, was an inaccurate placement of Christ's birth; if the description of a census is true, then Christ was born either several years before or, more probably, 3 years after 753.
Dionysius then began to reckon all later events in relation to 753 as years of "our lord," in Latin, anno domini, abbreviated A.D. In this manner, the Christian calendar was invented.
The idea of dating events from Christ's birth was spread when the new Easter tables Dionysius had constructed were propagated throughout Christendom. The Christian calendar was soon in use in Italy and Spain. The earliest recorded use of dating via anno domini was by Bede in the seventh century, after which its use picked up in England. Charlemagne is credited with being the first Christian ruler to use it in official records, in the 8th century. But it wasn't until the 10th century that the papal chancery began to employ the system.
Rather ironically, considering his great influence on systems of dating, the exact date of the death of Dionysius is unknown. He is believed to have died sometime before A.D. 544.
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