DIONYSIUS EXIGUUS, a scholar of the 6th century, was, according to the statement of his friend Cassiodorus, a Scythian by birth. He was living at Rome in the first half of the 6th century, and is usually spoken of as abbot of a Roman monastery though Cassiodorus calls him simply "monk." He was in high repute as a theologian, was profoundly versed in the Holy Scriptures and in canon law, and was also an accomplished mathematician and astronomer. We owe to him a collection of 401 ecclesiastical canons, including the apostolical canons and the decrees of the Councils of Nicaea, Constantinople, Chalcedon and Sardis, and also a collection of the decretals of the popes from Siricius (385) to Anastasius II. (498). These collections, which had great authority in the West (see CANON LAW), were published by Justel in 1628. Dionysius translated many Greek works now lost, including Life of St. Pachomius, and the Instruc tion of St. Proclus of Constantinople. He introduced the method of reckoning the Christian era which we now use (see CHRON OLOGY). He died at Rome, some time before A.D. 55o.