Dionysius Exiguus - Easter Tables

Easter Tables

In 525, Dionysius prepared a table of the future dates of Easter and a set of "arguments" explaining their calculation (computus) on his own initiative, at the request of Pope John I. Note well that only the first nine arguments are by Dionysius — arguments 10 to 16 as well as the second paragraphs of 3 and 4 and the third paragraph of 9 are later interpolations. Arguments 11 and 12 imply that these were interpolated in the year 675, shortly before Bede. He introduced his tables and arguments via a letter to a bishop Petronius (also written in 525) and added another explanatory letter (written in 526). These works in volume 67 of the 217 volume Patrologia Latina also include a letter from Bishop Proterius of Alexandria to Pope Leo (written before 457). Though not named by Dionysius, this collection was recently called his Liber de Paschate (Book on Easter) by Audette.

He ignored the existing tables used by the Church of Rome, which were prepared in 457 by Victorius of Aquitaine, complaining that they did not obey Alexandrian principles, without actually acknowledging their existence. To be sure that his own tables were correct, he simply extended a set of tables prepared in Alexandria that had circulated in the West in Latin, but were never used in the West to determine the date of Easter (however, they were used in the Byzantine Empire, in Greek). The Latin tables were prepared by a subordinate of Bishop Cyril of Alexandria shortly before Cyril's death in 444. They covered a period of 95 years or five decennovenal (19-year) cycles with years dated in the Diocletian Era, whose first year was 285 (the modern historical year in progress at Easter). Diocletian years were advantageous because their division by 19 yielded a remainder equal to the year of the decennovenal cycle (1–19).

Dionysius' tables were quickly adopted at Rome, and from this time the arguments between Rome and Alexandria regarding the correct date for the celebration of Easter came to an end - both used identical tables and hence observed the feast on the same day.

The epact (the age of the moon on 22 March) of all first decennovenal years was zero, making Dionysius the first known medieval Latin writer to use a precursor of the number zero. The Latin word nulla meaning no/none was used because no Roman numeral for zero existed. To determine the decennovenal year, the Dionysian year plus one was divided by 19. If the result was zero (to be replaced by 19), it was represented by the Latin word nihil, also meaning nothing. Both "zeros" continued to be used by (among others) Bede, by whose extension of Dionysius Exiguus’ Easter table to a great Easter cycle all future Julian calendar dates of Easter Sunday were fixed unambiguously at last. However, in medieval Europe one had to wait as late as the second millennium to see the number zero itself come into use, although it had come into being around the year 600 in India.

Dionysius copied the last decennovenal cycle of the Cyrillian table ending with Diocletian 247, and then added a new 95-year table with numbered Anni Domini Nostri Jesu Christi (Years of our Lord Jesus Christ) because, as he explained to Petronius, he did not wish to continue the memory of a tyrant who persecuted Christians. The only reason he gave for beginning his new 95-year table with the year 532 was that six years were still left in the Cyrillian table after the year during which he wrote. For the latter year he only stated that it was 525 years after the Incarnation of Christ, without stating when the latter event occurred in any other calendar. He did not realize that the dates of the Alexandrian Easter repeated after 532 years, despite his apparent knowledge of the Victorian 532-year 'cycle', indicating only that Easter did not repeat after 95 years. He knew that Victorian Easters did not agree with Alexandrian Easters, thus he no doubt assumed that they had no bearing on any Alexandrian cycle. Furthermore, he obviously did not realize that simply multiplying 19 by 4 by 7 (decennovenal cycle × cycle of leap years × days in a week) fixed the Alexandrian cycle at 532 years, otherwise he would have stated such a simple fact.

Most of the British Church accepted the Dionysian tables after the Synod of Whitby in 664, which agreed that the old British method (the insular latercus) should be dropped in favour of the Roman one. Quite a few individual churches and monasteries refused to accept them, the last holdout finally accepting them during the early 10th century. The Church of the Franks (France) accepted them during the late 8th century under the tutelage of Alcuin, after he arrived from Britain.

Ever since the 2nd century, some bishoprics in the Eastern Roman Empire had counted years from the birth of Christ, but there was no agreement on the correct epoch — Clement of Alexandria (c. 190) and Eusebius of Caesarea (c. 320) wrote about these attempts. Because Dionysius did not place the Incarnation in an explicit year, competent scholars have deduced both AD 1 and 1 BC. Most have selected 1 BC (historians do not use a year zero). Because the anniversary of the Incarnation was 25 March, which was near Easter, a year that was 525 years "since the Incarnation" implied that 525 whole years were completed near that Easter. Consequently one year since the Incarnation would have meant 25 March 1, meaning that Dionysius placed the Incarnation on 25 March 1 BC. Because the birth of Jesus was nine calendar months later, Dionysius implied, but never stated, that Jesus was born 25 December 1 BC. Only one scholar, Georges Declerq (Declerq, 2002), thinks that Dionysius placed the Incarnation and Nativity in AD 1, basing his conclusion on the structure of Dionysius's Easter tables. In either case, Dionysius ignored his predecessors, who usually placed the Nativity in the year we now label 2 BC. In his 1605 thesis, the Polish historian Laurentius Suslyga was the first to suggest that Christ was actually born around 4 BC, deriving this from the chronology of Herod the Great, his son Philip the Tetrarch, and the daughter of Augustus, Julia. Having read Suslyga's work, Kepler noted that Christ was born during the reign of King Herod the Great (2:1–18), whose death he placed in 4 BC. Kepler chose this year because Josephus stated that a lunar eclipse occurred shortly before Herod's death. John Pratt of the International Planetarium Society proposed the 29 December 1 BC eclipse as another eclipse. According to Josephus, Herod died in the year 4 or 3 BC.

Although Dionysius stated that the First Council of Nicaea in 325 sanctioned his method of dating Easter, the surviving documents are ambiguous. A canon of the council implied that the Roman and Alexandrian methods were the same even though they were not, whereas a delegate from Alexandria stated in a letter to his brethren that their method was supported by the council. In either case, Dionysius' method had actually been used by the Church of Alexandria (but not by the Church of Rome) at least as early as 311, and probably began during the first decade of the 4th century, its dates naturally being given in the Alexandrian calendar. Thus Dionysius did not develop a new method of dating Easter. The most that he may have done was convert its arguments from the Alexandrian calendar into the Julian calendar. The resulting Julian date for Easter was the Sunday following the first Luna XIV (the 14th day of the moon) that occurred on or after the XII Kalendas Aprilis (21 March) (12 days before the first of April, inclusive). The 14th day of the moon, Nisan 14, was the date that Paschal lambs were slain (in late afternoon) until the destruction of the Second Temple in 70 prevented their continuing sacrifice, as well as the day when all leavened bread crumbs had to be collected and burned, hence Nisan 14 was the day of preparation for Passover (Lev 23:5). Alexandria may have chosen it because it was the day that Christ was crucified according to the Gospel of John (18:28, 19:14), in direct contradiction to the Synoptic Gospels (Matthew 26:17, Mark 14:12, and Luke 22:7), who state that he was crucified after he ate the Seder, his Last Supper. Then and now, the Seder was eaten after sundown at the beginning of Nisan 15. Because Dionysius's method of computing Easter used dates in the Julian calendar, it is also called the Julian Easter. This Easter is still used by almost all Orthodox churches. The Gregorian Easter still uses the same definition, but relative to its own solar and lunar dates.