Most of us are already familiar with the Common Era (C.E.) as a secular version of the Anno Domini (A.D.) chronological system, which dates events according to “the Year of Our Lord,” or the birth of Jesus. But when exactly did people start dating things from the time of Christ? Obviously when Jesus was born no one had a calendar saying it was year 0. Herod had no way of knowing he came to power in the year 37 B.C. In fact, it was not until hundreds of years after the time of Jesus that anyone tried to reckon the years that had elapsed since his birth.
Most of the earliest Christians were converted Jews, who relied on the Jewish lunar calendar; but as Christianity spread to other groups, most people continued to use the Roman calendar introduced by Julius Caesar in 46 B.C.E. (Before the Common Era). Created with the help of the great Alexandrian astronomer Sosigenes, Caesar’s “Julian” calendar formally established a solar year measuring 12 months or 365 1/4 days. (The quarter was made up in an extra day every fourth or “leap” year.)
While the Julian Calendar effectively standardized the length of the year throughout the Roman Empire—and made it easy to refer to a particular date within a given year—a variety of options were still available for distinguishing one year from another. The Romans frequently referred to a particular year by the names of the consuls who had ruled at the time. Roman historians sometimes also numbered years from “the founding of the city of Rome” (ab urba condita) in what we would call 753 B.C.E. A third way of numbering years was by fixing them in relation to the Indiction, or 15-year tax cycle.
In the fourth century, many Christians began situating themselves within the “Era of the Martyrs,” which started in 284 C.E., with the Roman emperor Diocletian’s persecution of Christians. Citizens of Antioch in Syria pegged “year 1” to 49 B.C.E. in commemoration of Julius Caesar’s dictatorship. In the fifth century many Greek-speaking Christians started to number years from the creation of the world (Anno Mundi), which they believed occurred in either 5493 or 5509 B.C.E. By the tenth century C.E., Anno Mundi dating—with the world’s creation fixed at 5509 B.C.E.—became standard in the Byzantine Empire and hence in the Orthodox countries of Eastern Europe.
The first person to number years from the birth of Jesus was a scholar and abbot named Dionysius Exiguus (Denis the Little), who lived in Rome in the sixth century C.E. When the church timetable used for calculating the correct 007date of Easter was about to run out, the Pope asked Dionysius to extend it. Finding the exact date of Easter was always problematic for church officials because they relied on the Roman solar calendar, whereas the anniversary of Christ’s death and resurrection were supposed to take place after the Passover festival, which was grounded on the Jewish lunar calendar. While figuring out the chronological details for his Easter Table, Dionysius counted backwards and established what he thought was the year of the birth or “Incarnation” of Christ. (He was off by at least four years. Modern scholars think that Jesus was actually born between 4 and 7 B.C.E.) Dionysius used his chronology to label the then current year Anno Domini Nostri Jesu Christi (the Year of Our Lord Jesus Christ) 532.
Dionysius’s invention did not spread like wildfire. Even Dionysius did not use it all the time. The greatest advocate of the A.D. dating system was the great English churchman and historian, the Venerable Bede (673–735). Bede systematically used A.D. to describe the whole history of England. His history was very influential in Europe and his style of dating started to be used in French-speaking regions in the eighth century and in Germany in the ninth century. The Catholic Church was not in the vanguard of the Anno Domini system, but used both A.D. dates and the regnal years of the Popes until the 15th century.
While the A.D. system spread throughout Europe during the Middle Ages, the basic calendar in use was still Julius Caesar’s. But the Julian Calendar’s reckoning of 365 1/4; days in one solar year was too long by 11 minutes and 14 seconds each year. This meant that over time astronomical phenomena fell out of sync with their fixed dates in the calendar. By the 16th century, the spring equinox occurred ten days before March 21!
In the 1570s a group of church astronomers, led by the Jesuit scholar Christopher Clavius (1537–1612), recalculated the length of the solar year and arrived at a more precise estimate of 365.2422 days. (Their estimate was remarkably accurate; modern scientists calculate the year as 365.242199 days.) Since the difference between the Jesuit solar year (365.242 days) and the Julian year (365.25 days) added up to a total of 3.12 days every 400 years, the Jesuits proposed that three out of every four centennial years should no longer be leap years. (For example, the centennial years 1700, 1800 and 1900 were not leap years, but the year 2000 will be one.) This modification to the Julian system saves three days every four centuries and ensures that the modern calendar loses only .0003 days each year.
In 1582, Pope Gregory XIII issued a papal bull officially adopting the Jesuit calendar reforms. To eliminate the already existing time lag between astronomical phenomena and their fixed dates, he also cut ten days out of October that year. By papal decree, October 4 was followed by October 15, 1582.
Unfortunately, Gregory’s reforms were ill-timed. At the moment of his decree, much of Europe was embroiled in the Wars of Religion (1562–1598) and a good many people in Europe (to say nothing of the rest of the world) were unwilling to change their calendars just because the Pope said so. While the new Gregorian calendar was adopted fairly quickly by the Catholic countries of Europe, the German Protestant nations refused to accept Gregory’s reforms until 1699. England clung to the Julian calendar until 1752!
With the onset of Western colonization and increased international trade, the Gregorian Calendar started to gain a foothold in non-Western countries in the late 19th century. Japan was the first Asian country to adopt it in 1873. The upheavals of the First World War accelerated the process, with most eastern European and East Asian countries falling into line between 1912 and 1918. Greece—and the Eastern Orthodox Church—eventually also adopted a modified version of the Gregorian calendar in 1923.
Of course, all of this leads us to one final question. If we’re numbering years according to the life of Jesus, why don’t we celebrate New Year’s Eve with Christ’s birth on December 25, or with the date of his conception on March 25 (which also coincides with the arrival of Spring)? As it happened, both of these dates were popular days for celebrating the beginning of the New Year throughout the Middle Ages. January 1 only became universally recognized as New Year’s Day with the general adoption of the Gregorian calendar. So if you can’t find a baby sitter for December 31, you can always celebrate on March 25. And if you’re sick of the whole thing you could use Byzantine Time and say it’s Anno Mundi 7509.
Most of us are already familiar with the Common Era (C.E.) as a secular version of the Anno Domini (A.D.) chronological system, which dates events according to “the Year of Our Lord,” or the birth of Jesus. But when exactly did people start dating things from the time of Christ? Obviously when Jesus was born no one had a calendar saying it was year 0. Herod had no way of knowing he came to power in the year 37 B.C. In fact, it was not until hundreds of years after the time of Jesus that anyone tried to reckon […]