We celebrated our New Year on January 1 but the Chinese will do so this month. Why the difference?
In 2018 the Chinese celebrate New Year on February 16. It changes slightly from year to year because China has a lunar calendar that keeps in phase with the seasons. Each month starts with a new moon, and ever since a calendar reform in 104 BC they have taken the first month of the year to start with the second new moon after the winter equinox. Diaries based on Western Europe or the USA show this to be February 15 this year, but the Chinese calendar is based on Beijing where it will already be the 16th.
For any culture using a lunar calendar, the new year will occur on varying dates in our standard international calendar because a seasonal year does not contain a whole number of lunar months. It contains between 12 and 13 (12 months is about 354.37 days), so to keep in phase with the seasons some years must contain 13 lunar months rather than 12. The Islamic calendar ignores this difficulty by having 12 lunar months every year, which is why the holy month of Ramadan starts about 11 days earlier each year — this year it will begin on the evening of May 15.
Judaism also has a lunar calendar, months starting with the new crescent of the moon, as in the Islamic system. A new crescent can only occur in the evening, which is why Jewish and Islamic months and days start in the evening. Yet like the Chinese calendar the Jewish one keeps in phase with the seasons, some years having 12 months, some 13. Unlike China, however, the Jewish New Year begins in the autumn and is associated with the harvest — the next one starts on the evening of September 9, 2018.
Early calendars would have been lunar, and 12 months per year suggests this was the origin of our modern international calendar — indeed, the very word month is related to the word for moon. It started with the Roman Republic, where a later tradition claimed the early kings of Rome created a lunar calendar, although records from 400 BC show it had already lost its connection with the moon’s phases. However, its 12 months retained the lunar feature of adding up to 355 days (354 is closer but the Romans had a preference for odd numbers), and to keep it in phase with the seasonal year they added extra days from time to time, inserting them into February. The decision on whether or not to do this was the job of a committee subject to political influence, and by the time Julius Caesar decided to fix the calendar it was 80 days out of phase with the seasonal year.
To reform it he created a 365-day year, using the same month names, with a leap year every four years, and extended the year 46 BC to get back in phase with the seasons. This new “Julian calendar” started running on the new terms in 45 BC, the year before Caesar’s assassination.
The start of the year was originally in March, named after Mars the god of war, when military manoeuvres would begin again, and the months from July to December were named after the numbers five to ten, though the Senate later renamed Quintilis (five) and Sextilis (six) in honour of the emperors Julius and Augustus. As for January and February, an old Roman tradition claimed that Romulus had originally devised a year of ten lunar months, which ended with December and started up again the following March.
Whatever the truth of such legends, springtime is a natural season to start a year, and New Year’s day in the modern Persian calendar occurs on March 21, the day of the spring equinox.
The Julian calendar, used in Britain until 1752, would change from one year to the next on March 25, the day of the Annunciation and nine months before the birth of Jesus on Christmas Day. Thus March 24, 1750, was followed by March 25, 1751, and a glance at an early 18th-century book of chronology shows the death of King Edward the Confessor in January 1065, with the Battle of Hastings in October 1066. In our present dating system both were the same year. At one time March 25 was reckoned to be the spring equinox, but it was slowly shifting because the Julian year is slightly too long and during late medieval times scholars wanted to fix the problem. Changing a calendar is a task for the all-powerful, an emperor in the case of the Julian calendar and a pope in the case of its amendment to the Gregorian calendar (named after Pope Gregory XIII) in 1582.
That change involved removing ten days from the year, slightly amending the frequency of leap years (there will not be one in 2100 for example), and moving the start of the year to January 1. The Protestant world naturally declined to follow Papist rules, and Britain only adopted the Gregorian calendar in 1752. By that time we had to remove 11 days from the year (because 1700 had not been a leap year in the new calendar), and “Give us our 11 days” became a street slogan during calendar riots at the time — if you believed your date of death was foretold, you lost 11 days of life. Adding these 11 days to the British tax year, which had always run from March 25 to March 24, now made it run from April 5 to April 4. Nearly half a century later the absence of a leap year in 1800 caused the authorities to move it forward another day from April 6 to April 5, where it has remained ever since.
Meanwhile, the Chinese calendar adhered to rules laid down long before, as did the Jewish calendar, which was adopted from Babylonia. Astronomers in both places had long ago noticed that 19 seasonal years were approximately 235 lunar months, and both societies regulated their calendar on a 19-year cycle, with seven long years of 13 months each and 12 short years of 12 months each, cycles that are still in use today.