I’m writing a story where one of the major plot pivots is the shift from the Julian to the Gregorian calendar, an event that (possibly) caused riots in Britain in the 18th century.

Running an empire on Bula time

Julius Caesar established the Julian calendar, in 46 BC. It was a reform of the Roman calendar, which was so complicated it had a committee to keep it in tune with the actual solar year. They would decide when to add or remove days, which made it hard to plan anything with precision.  Caesar wanted a system that didn’t change from year to year, and he employed an astronomer to create a calendar based entirely on the length of time the earth takes to go around the sun.

What makes the calculation tricky is that this revolution isn’t an exact number of days.  It takes, on average, 365 days, 5 hours, 48 minutes and 45 seconds for the earth to go around the sun. So Caesar’s astronomer hit on the idea of a 365 day year, with an extra day in February every four years.

A Feast day in Spring

As it turned out, a day every four years is too many, and by the sixteenth century, one of the most important feast days of the church — Easter — was in danger of losing its (Northern hemisphere) connection to Spring. Pope Gregory XIII hired an Italian scientist to fix the problem. Aloysus Lilius devised the variation we use today. In the Gregorian calculation, we add a leap day if the year can be divided by four, but not if it can also be divided by 100. However, if the year can also be divided by 400, in goes the leap day.

It isn’t perfect. In another 2,000 years, we’ll be a day out again. But it’s a lot closer.

No Papists messing with our calendar!

Pope Gregory’s reform took effect as soon as his proclamation went out, not only establishing the new system but making a one-off change — a jump of more than a week — to realign the dates with the seasons.

Italy, Spain, Portugal, and other Catholic countries all adopted the new calendar. European Protestants, however, saw the change as some kind of a plot, and refused to have anything to do with it. But one by one in the eighteenth century, common sense, trade, and political links prevailed.

No messing with our tax year!

Many of the German states switched early in the century. England changed in September 1752. The Calendar Act (an Act for Regulating the Commencement of the Year and for Correcting the Calendar now in Use) was introduced in 1751, passed through Parliament, and was signed into law in May 1752. Not only did it provide for 2nd September 1752 to be followed by 14th September 1752, but it also moved New Year’s Day from 25th March to 1st January. The previous New Year’s Day was the Feast of the Annunciation, and so Lady’s Day, and traditionally the day for paying taxes and rents. Changing the date of the tax payment would have shorted that tax year, so while the calendar year now started on January 1st, the start of the financial year remained as 5th April, or 25th March under the Julian Calendar. It was changed to 6th April in 1800 (which would have been a leap year under the Julian, but wasn’t), and 6th April it remains in Britain to this day.

The rioting was probably a myth

People were upset about the change, fearing that the government was taking 11 days off their lives. But the story that there were riots is not borne out by newspapers and other contemporary accounts. Possibly it comes from the Hogarth painting of an election meeting, shown above. The calendar reform was an election campaign topic in 1754, and the painting shows a demonstration outside the window. You can just see a sign saying ‘Give us our 11 days’.