The monk who accidentally invented our modern calendar to avoid a tyrant's memory

Ideas & Philosophy · Published 3 October 2026 Swipe more like this →

In short: Dionysius Exiguus, a 6th-century monk, sought to replace the Diocletian calendar because he despised the emperor who persecuted Christians. By anchoring time to the incarnation of Jesus, he created the Anno Domini system. Yet, he never intended it for history—only for calculating the correct date of Easter.

Born in Scythia Minor around 470, Dionysius lived in Rome from roughly 500 until his death around 544. While often labeled a 'Scythian,' this term was geographically imprecise, likely referring to his origins in the Latinized Danubian provinces rather than an ethnic identity. He was a prolific translator, rendering Greek church canons and theological works into Latin, which cemented his influence on Western ecclesiastical administration for centuries.

His most enduring legacy, the Anno Domini (AD) era, emerged from a technical necessity. In 525, Pope John I requested a new Easter table to resolve discrepancies in existing calculations. Dionysius rejected the prevailing Diocletian era, which counted years from the start of Diocletian's reign in 285, because he refused to honor a tyrant. Instead, he calculated his table based on the 'incarnation of our Lord Jesus Christ,' identifying the current year as 525. He did not explicitly define the epoch of the Incarnation, leading to ongoing scholarly debate over whether he intended AD 1 or 1 BC.

Dionysius did not invent the method for calculating Easter; he adapted Alexandrian principles that had circulated in the East. His innovation was converting these complex calculations into the Julian calendar. Because he lacked a concept for the number zero, he used the Latin word 'nulla' to represent the absence of a value in his cycles. His system faced resistance, only gaining widespread acceptance in Britain after the Synod of Whitby in 664 and in France during the late 8th century.

The motivation behind his work was partly theological. Some contemporaries feared the end of the world was imminent, believing the year 6000 of the Anno Mundi calendar would mark the Second Coming. By shifting the focus to the Incarnation, Dionysius provided a new framework that moved away from these apocalyptic expectations. Though he never used his system to date historical events, his Easter table became the foundation for the Gregorian and Julian calendars we use today.

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