24 February: Calendars

Gregorian Calendar Day: Pope Gregory XIII issued a papal bull in 1582 adopting the Gregorian calendar. It is the most widely used calendar in the world today and was named after him. 10 things you didn't know about calendars.

1. The Gregorian calendar wasn't popular with everyone at first, even though it was more accurate than any other calendars in use at the time, differing from the solar year by just 26 seconds. Because it was being promoted by a pope, non-Catholic countries didn't get on board because they believed at best that the pope was trying to control them and at worst that this new fangled calendar was the work of the Devil or the Antichrist.
2. For this reason Germany didn't start using it until 1700 and the UK until 1752. Greece didn't start using the Gregorian calendar until 1923.
3. Gregory's main reason for introducing a new calendar was to make sure that Easter fell in Spring each year.
4. Regular readers of this blog will know that I sometimes use celebrations from the French Revolutionary Calendar. This calendar was devised because the French didn't want to use the calendar the pope was proposing and came up with their own. It was a secular calendar attempting to decimalise time. It had twelve months of 30 days, named after weather and nature appropriate to the season (eg "Brumaire" meaning fog, which began towards the end of October). It was divided into 10 day weeks called décades. The Catholic church had a saint assigned to each day, and the French calendar wanted to get away from that, too, so instead, they assigned a plant, animal, tool or substance important to the rural economy to each day of the year.
5. Talking of weeks, why does a week have seven days? We have the ancient Babylonians to thank for that - they observed a holy day every seven days. Days of the week were named after the Sun, the Moon and the five planets known before telescopes were invented, which all corresponded to a deity - the Romans named them for their gods Mars, Mercury, Jupiter, Venus and Saturn. That explains Saturday, Sunday and Monday and the names for days of the week in other languages (eg Mardi and Mercredi which are the French words for Tuesday and Wednesday). Tuesday, Wednesday, Thursday and Friday come from the Germanic and Norse deities Tiw, Woden, Thor and Freia.
6. Ancient peoples first measured time by observing the phases of the moon. This is where the word month comes from. It was important to them because they needed to know when to plant and harvest crops and keep track of their animals. The Ancient Egyptians deemed the year to begin on the day that the star Sirius (which they associated with the goddess Isis) rose with the sun, which it does every 365.24 days.
7. No calendar has ever been completely accurate, because there are so many factors at play - the seasons, the rotation of the Earth, its orbit around the sun and so on. Most calendars have to factor in something called "intercalary" days so that the calendar and the seasons remain in synch. This is what February 29 in Leap years is for. However, even that doesn't solve the problem entirely, as a tropical year, the time it takes the Earth to go around the sun, isn't exactly 365.25 days. Hence every fourth year is a leap year, but every 100 years, if the year isn't divisible by 400 as well, we don't have a leap year. 1900 wasn't a leap year, but 2000 was. Other cultures came up with different solutions. The Mayans, for example, had five intercalary days which they believed were unlucky. Other calendars added a thirteenth month every few years.
8. Muslims use a different calendar which is a lunar calendar, based on the phases of the moon. They don't use intercalary days. That's why the festival of Ramadan doesn't happen at exactly the same season every year.
9. When Britain adopted the Gregorian calendar in 1752, the date jumped from September 2nd to September 14th. It's often said that the British people took to the streets and rioted because they believed the government were taking away eleven days of their lives. While Brexit proves that large numbers of British people probably are that stupid, historians now reckon that the ordinary people accepted the change more readily than previously thought.
10. It was at this time, too, that New Year began to be celebrated on January 1st. Before this, March 25th, aka Lady Day or the feast of the Annunciation, a celebration of the Virgin Mary, was New Year's Day in Britain. It was Julius Caesar who first selected January 1st as the first day of the year.