Where the error came from
The old calendar assumed that a year had exactly 365 and a quarter days. In reality, the year is slightly shorter. The difference is about 11 minutes, a small error that adds up to almost a day over a century.
The problem was not inconvenience but the church calendar. The date of Easter is tied to the spring equinox, and the equinox was slowly drifting away from its calendar date. By the 16th century, the gap was obvious to everyone.
- 1582Reform: October 4 was followed by October 15. The rule for leap years changed too.
- 16th-17th centuriesCatholic countries switched almost immediately, while Protestant and Orthodox countries did not: the issue was seen as more than just a matter of counting.
- 1752Britain and its colonies switched, dropping 11 days by then: the gap had grown in the meantime.
- 20th centuryThe last countries switched to the new system; by then, the difference had reached 13 days.
The new rule is simple: a year is not a leap year if it is divisible by 100, but it is a leap year if it is divisible by 400. Three extra days are removed every 400 years, and the calendar matches Earth's movement again.
What happened next
People took to the streets demanding that their stolen days of life be returned.
Historians find no evidence of such riots. There was discontent, but it concerned rent deadlines, interest, wages, and church holidays. In other words, it was about practical matters.
The practical questions really were complicated. People had to decide whether payment was due for the days that were dropped, when a contract deadline took effect, and how to calculate age. Separate laws were needed to settle these issues.
Because countries switched at different times, double dating continued for a long time. Letters and contracts were signed with two dates at once, and a traveler crossing a border changed the date along with the country.
This also caused confusion with historical dates. The same event may be dated differently in different sources, so historians have to clarify each time which calendar the date uses.
Why were 10 days removed from the calendar?
Is it true that people rioted, demanding that the days be returned?
Sources
- The Gregorian reform of 1582 eliminated the accumulated discrepancy between the Julian calendar and the tropical year: October 4 was followed by October 15, and the rule for leap years was changed. Countries switched to the new system at different times
- in Britain, 11 days were omitted in 1752. Historians find no evidence of mass riots demanding that the days be returned
- the known protests were connected with contract calculations and the church calendar
Next in the “Inventions” series
2 articles in full on the site, 3 more in the app
