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Dionysius Exiguus(dīənĭsh`ēəs ĕksĭg`yo͞oəs), d. c.545, Roman monk, chronologist, and scholar, a transmitter of Greek thought to the Middle Ages. He made collections of 5th-century papal decretals and the canons of the early church councils. Dionysius, in an attempt to improve the reckoning of the date of Easter, was the first (525) to use our present system of reckoning a date from the time of the birth of Jesus (see eraera,
period of historic time. In geology, it is the name applied to large divisions of geological process, e.g., Paleozoic era (see geology). In chronology an era is a period reckoned from a fixed point in time, as before or after the birth of Christ—before Christ, B.C.
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