By Tom Anderson
“Did you hear about the man who stole a calendar? He got twelve months.”
– old Christmas cracker joke
Since the dawn of human civilisation, the problem of telling time has been a puzzle for the wisest in society. Long before we cared about hours, minutes or seconds (or had clocks capable of measuring them), understanding the year was the key challenge. This was not some intellectual problem to be considered for its own sake, but vital for the future of cities and empires. The Ancient Egyptians, for example, established a solar calendar to predict when the Nile would rise to irrigate their fields, so they could prepare for it. This was calculated based on the summer rising of Sirius, the Dog Star (which for the ancient Greeks also gave its name to the sultry ‘dog days’ of summer). The Egyptian year was divided into three seasons, Flood, Emergence and Harvest, which were in turn divided into four months each of 30 days.
This was a problem, because years and days (unlike hours or weeks) are not arbitrary, human-defined divisions of time, but reflect an objective reality. A year is the time in which the Earth orbits the Sun, passing through its seasons (caused by differential sunlight falling on each hemisphere of the tilted Earth) and then resetting to the start of the year. A day is the time it takes the Earth to rotate on its axis once, which from the perspective of dwellers on the Earth appears to reflect the Sun rising, setting and returning after the hours of night. The Earth rotates on its axis approximately 365 and a quarter times in one orbit—not a number that readily divides up! The Egyptian calendar was called the ‘wandering calendar’ because its length did not match up with the year length. Additional intercalary days were added to try to fix this, but the calendar still rotated by about one day every five years. In 238 BC the Pharoah Ptolemy III attempted a correction, but this was resisted by the priesthood—a recurring theme we will see throughout history.
Some calendars are based on the motion of the Moon rather than the Sun. The Moon takes 29 and one-half days to orbit the Earth and pass through all its phases; this is therefore seen as the default length for a month (whose name is related to the word ‘moon’). 12 of these cycles equates to 354 days and eight hours, lacking 11 days relative to a solar calendar. These calendars are often called ‘lunar calendars’, but properly they should be ‘lunisolar calendars’, as there is usually some correction applied to bring them into line with the solar year. Exactly what form this takes depends on the calendar, and there are many.
There are almost as many calendars as there are civilisations. Probably the best-known non-Western calendar in the West is the Chinese calendar, a lunisolar construction which puts New Year on the first New Moon after the winter solstice (21st December by the Western calendar). This usually falls in late January or early February. Of course, these months are not used in the Chinese calendar, which instead has 12 lunar months—which, in the different naming systems, are named either after characteristic plants and flowers, the signs of the Chinese zodiac, or simply numbered. Other calendars derived from the Chinese one are or were used in countries such as Vietnam, Japan and Korea, sometimes being replaced with the Western Gregorian calendar and now only used for festivals. What is usually called ‘Chinese New Year’ in the West is really more generally known as ‘Lunar New Year’, and is celebrated as the New Year by many people far beyond China.
The Hebrew and Islamic calendars are also lunar-based, but define New Year differently. Several definitions are used in the Hebrew calendar for different purposes (which can be considered similar to how the modern British calendar has both calendar years starting on January 1st, but also academic years starting in September and fiscal years starting in April). Islamic New Year is the first day of the month of Muharram and based on astronomical calculations, counting the years since Muhammad emigrated from Mecca to Medina. Unlike many lunar calendars, the Islamic calendar is not (consistently) corrected by intercalation (which is theoretically forbidden in the Qur’an) but instead simply travels through a 33-year cycle before re-synchronising with the solar year.
The Western calendar as we know it began in Ancient Rome. The early Romans used a lunar calendar together with an eight-day week (seven days, of Greek origin, was far from universal—the Chinese also used a ten-day week at this time). Originally, the calendar was divided into ten months beginning in March (named for the war god Mars) and ending in December (whose name means ‘tenth’), with ‘winter’ as an undefined additional number of days between December and Mars. This period was later divided into January and February, named for the two-faced god Janus and a word meaning a period of purification, respectively. This calendar was severely flawed and required constant intercalation and modification to stay in time with the solar year. Intercalated days were added to the month of February, the month of purification, for superstitious reasons. When Rome became a republic and elected consuls to six-month terms based on the calendar, crafty politicians began tinkering with the intercalation to increase their allies’ terms in office and reduce their opponents’ ones! This tactic is one which, fortunately, does not yet appear to have occurred to the United States Congress.
Julius Caesar became Pontifex (chief priest of Rome) as part of his political ambitions, and used this power to properly reform the calendar in 45 BC. His aim was to create a calendar that would remain aligned to the Sun, without any additional (fallible) human intervention required. Caesar drew upon the learning of Greek mathematicians and astronomers such as Sosigenes of Alexandria, who had calculated the precise length of the solar year. Caesar’s new calendar, called the Julian Calendar, was a compromise between the Roman month names, the fixed length of the Egyptian year, and the the Greeks’ scientific observations—a triumph illustrating how his remarkable life had led him throughout the entire Roman world and been exposed to diverse forms of learning. Under his system, a single leap day would be added to every fourth year, called a leap year. Because of the old Roman superstitions about February, this would be added to the end of that month—as it still is today! The additional day equated to the four quarter days missed out by having only a 365-day calendar year when the solar year was 365 and a quarter days. The system worked well, it seemed.
Caesar also realigned the year so that it would begin on January 1st, but this did not always take; Middle Ages Europe would continue to use his calendar, but often start the year formally on either Christmas Day (the Nativity of Jesus) or March 25th (the traditional date of the Incarnation of Jesus). In England and Britain, March 25th was used in between 1155 and 1754, when it returned to January 1st. Ironically, the eventual return of January 1st as New Year’s Day therefore reflects Caesar’s original intentions.
The Julian Calendar was so successful that, originally intended only for the city of Rome, it was adopted in modified forms across much of the Old World. It was not perfect, however. The Greeks were aware that a small discrepency remained because the solar year is not quite exactly 365 and a quarter days. The Earth’s orbit desynchronises compared to the Julian calendar by 11 minutes every year—a very small difference compared to the vast problems Caesar had fixed, but one which gradually built up as the calendar was used for centuries. The calendar gained a day every 128 years, which caused problems for the Catholic Church. Setting the date of Easter (an act called the computus) is a challenge which much mathematical ingenuity was devoted to. Christ’s death and resurrection occurred at the time of the Jewish Passover, but (as noted above) the Hebrew calendar is lunar and does not synchronise with the solar calendar. The Council of Nicaea in AD 325 had recommended that all Christians should celebrate Easter on the same day, but setting such a day was contentious. Christians began to regard the Jews’ calculations as being in error, and wanted an objective way of setting the date of Easter in relation to the Spring Equinox. Unfortunately, due to the small flaw in the Julian calendar, this date wandered; the increasing desynchronisation was noted by writers such as the Venerable Bede, Roger Bacon and Dante Alighieri over the years.
Pope Gregory XIII finally grasped the nettle of reform in 1582. He implemented the new Gregorian Calendar, still used today. He dealt with the now eleven-day deficit in one fell swoop by proclaiming that October 4th 1582 should be followed immediately by October 15th 1582. To ensure the deficit should not return, the new calendar imposed the rule that leap years would not take place in years divisible by 100, unless they were also divisible by 400. So 1700, 1800 and 1900 were not leap years, but 1600 and 2000 were. The result is a calendar so accurate that more problems are caused by astronomical variations (the Earth’s rotating is gradually slowing down) than by human error—a remarkable feat for sixteenth-century science!
Nonetheless, Gregory and his experts (principally Aloysius Lilius and Christopher Clavius) were unfortunate enough to deliver this breakthrough at a time when the Reformation meant that Papal pronouncements were regarded as suspicious and tainted outside the Catholic world. For this reason, it took centuries for the rest of the Julian world to switch over to the improved Gregorian calendar. In Britain, this took place in 1752, where September 2nd was followed immediately by September 14th. This was criticised by the opposition Tories as the adoption of a ‘popish’ calendar, memorably recorded in Hogarth’s “Humours of an Election”, in which Tory supporters in the general election of 1754 are shown with a banner reading “Give us (back) our eleven days!” However, there is little evidence of any superstitious rioting over the move as is sometimes claimed—though there were genuine concerns of potential upsets to rent calculations, a concern that returned for the question of decimalisation in the twentieth century. British (and American) dates of the eighteenth century are frequently appended ‘O.S.’ or ‘N.S.’ to clarify whether it means Old Style or New Style dating.
Orthodox Russia continued to use the Julian calendar until the Revolution in 1917. The gap between the calendars meant that (confusingly) the February Revolution of Kerensky took place in March (by the Gregorian calendar used elsewhere) and Red October took place in November!
Once one has settled on a counting system, of course, there is the question of where to calculate Year 1 from (there is no Year 0). The original Julian calendar, like its flawed Roman predecessor, counted from the legendary foundation of Rome in 753 BC; these years were abbreviated Anno urbis conditae or AUC, meaning ‘in the year since the City’s founding’. The later Byzantine remnant of the Roman Empire counted years from the calculated year of the creation of the world, which they placed 5509 years before Christ. The Jewish writer Maimonides made a different calculation of the same date and put it 3760 years before Christ. Historically, Jews instead often dated years from a significant event such as the Exodus or the destruction of the Temple in Jerusalem. Muslims, as noted above, number their years from Muhammad’s flight from Mecca in AD 622. Many civilisations, such as the Chinese, typically have not used a cumulative year numbering system but have instead reset the years on the accession of a new monarch—a system also used in the West at times, for example when referencing British laws.
This means that the year 2019 AD of the Christian era (Anno Domini, ‘in the Year of Our Lord’), which we are about to leave, is also the year 2772 AUC of the Romans, the year 7527 of the Byzantines, the year 1440 of the Muslims, the year 5779 of the Jews, and many more. This also ignores the fact that those calendars do not all start on the same day, so that the years do not synchronise so neatly. Telling the time is complicated!
2020 will also be the fifth year of Sea Lion Press since our foundation in 2015. What does the future hold? Let’s find out!
Tom Anderson is the author of SLP books including the Look To The West series (Diverge and Conquer, Uncharted Territory, Equal and Opposite Reactions), The Twilight's Last Gleaming, Not An English Word, The Curse of Maggie, The Unreformed Kingdom, and The Surly Bonds of Earth