Biographical Encyclopedia of Astronomers

2014 Edition
| Editors: Thomas Hockey, Virginia Trimble, Thomas R. Williams, Katherine Bracher, Richard A. Jarrell, Jordan D. MarchéII, JoAnn Palmeri, Daniel W. E. Green

Dionysius Exiguus

  • John M. McMahon
Reference work entry

Born Scythia Minor (Dobrudscha, Romania), mid to late fifth century

Died possibly Rome, (Italy), before 556

Dionysius, a monk of Scythian (or Gothic) birth educated in the ecclesiastical tradition on the west coast of the Black Sea, came to Rome sometime after 496, perhaps having earlier resided in Constantinople. Self-styled Exiguus (“the Slight”) out of intellectual humility, he was nevertheless an important figure in the canon law, theology, and computistics of Late Antiquity. Skilled in both Latin and Greek, Dionysius was instrumental in the translation of numerous Greek texts into Latin, including documents from the Church councils of Nicaea (325) and Chalcedon (451), along with a wide variety of theological treatises and ecclesiastical records. He was highly regarded by his contemporaries, especially by his friend   Cassiodorus .

Despite his monumental work in the ecclesiastical sphere, Dionysius is best remembered for his reworking of the Christian calendar. Petitioned by many contemporary clerics in the Church hierarchy, in 525 he undertook the calculations needed to extend for another 95 years the Easter table of Cyril of Alexandria, which spanned the years 437–531. In doing so Dionysius cited the Council of Nicaea’s authority in establishing a 19-year luni-solar cycle as the basis for determining the date of Easter and thus guaranteed in the West the acceptance of the Alexandrian method of reckoning the feast date. His work also drew upon and refined the earlier Easter calculations by Victorius, Bishop of Aquitaine, who had established the Paschal Cycle of 532 years (published in 465). Dionysius’s table itself was a modified version of Cyril’s original, and comprised eight columns, in several of which there was specified lunar and calendrical information, expressed in the Roman manner of Kalends, Nones, and Ides. The actual date of the Easter feast was put in the far right column. In addition, nine arithmetical argumenta, or shortcuts for calculation, were appended to the table, as was a letter to an otherwise unknown bishop Petronius explaining the tables and their calculations.

As part of these chronological recalculations, Dionysius also initiated a new method of counting the years. Since the earlier Cyrillan cycle had used the imperial Roman yearly dating system starting in 284 (the ascension of the Emperor Diocletian, a notorious persecutor of Christians), Dionysius abandoned it and started numbering years with the birth of Christ. Thus, he introduced the phrase Anno Domini(“In the year of the Lord”), which was incorporated into the Easter table. Yet while the table itself was effective in extending the Cyrillan Cycle, the new system of dating was not perfect. Lacking the concept of 0, Dionysius began the system with the year 1, making the first year of his table 532. Moreover, Dionysius had relied for the date of the Incarnation on Clement of Alexandria, who stated that it occurred in the 28th year of the reign of Augustus. But Dionysius mistakenly assumed that Augustus had counted his regnal years from his official assumption of power in 27 BCE. In fact, they were counted from the battle of Actium in 31 BCE. Uncertainty about the founding date of Rome, which served as the dating system in early imperial times, may also have been a source of some confusion. As a result, Dionysius’s entire dating system was inaccurate by 4 years.

Dionysius’s new dating system was not readily adopted. Although Cassiodorus used it in 562 for the Computus paschalis, and   Isidore knew of it (Etymologiae6.17), it gained support only slowly. Its wider acceptance began when the British cleric and historian   Bede incorporated it into his own works, De temporibus(On Times, 703), and De temporum ratione(On the rechoning of times, 725). Gradually, and because of the authority of Bede in later centuries, Dionysius’s system of dating spread throughout Europe.

Selected References

  1. Declercq, G. (2000). Anno Domini: The Origins of the Christian Era. Turnhout: Brepols, esp. pp. 97–147.Google Scholar
  2. Duncan, David E. (1998). Calendar: Humanity’s Epic Struggle to Determine a True and Accurate Year. New York: Bard, pp. 71–75.Google Scholar
  3. Migne, J. P. (1865). Patrologia Latina. Vol. 67, cols. 483–508. Paris: Migne (For the Latin texts of Dionysius’s Liber de Paschateand related texts.)Google Scholar
  4. Richards, E. G. (1998). Mapping Time: The Calendar and Its History. Oxford: Oxford University Press, pp. 217–218, 350–351.Google Scholar
  5. Teres, Gustav (1984). “Time Computations and Dionysius Exiguus.” Journal for the History of Astronomy15: 177–188.ADSMathSciNetCrossRefGoogle Scholar
  6. Wallis, Faith (1999). Bede: The Reckoning of Time. 2 Vols. Liverpool: Liverpool University Press, pp. liii–lv, 333–338, 347–348.Google Scholar

Copyright information

© Springer Science+Business Media New York 2014

Authors and Affiliations

  1. 1.Lemoyne UniversitySyracuseUSA