On February 5, 1582, the Gregorian calendar came into effect in Alsace. Yes, I say in Alsace, because France, Spain, Italy and Portugal had already switched to the Gregorian calendar more than 3 months ago.
There weren’t that many differences with the old Julian calendar, except that there was a gap… of ten days! These 10 days made it possible to immediately catch up with the delay taken by the old Julian calendar on the dates of the equinoxes since the Council of Nicaea, more than 1200 years before. Nine leap years had been counted too many, it was still nerd. It was also necessary to find the concordance between the spring equinox and March 21 on the calendar.
And here is the application of this famous Gregorian shift, so imagine yourself living in 1582, it’s February 5, you go to sleep and presto! The next day is not February 6 but February 16!
Historians call this bizarre moment the long night of February 5-16. Ten days: gone! In his Essays, even Montaigne, a cultivated man if ever there was one, mentions the difficulties that his contemporaries experienced in moving gradually to the new calendar and that he himself experienced in calculating his age. Some countries have been quite stubborn.
The prize goes to the Russians who kept the old calendar until 1918, can you imagine for dates? And birthdays? Does it count if the date never happened? I’m not even talking about international trade. So let’s have a thought for all those Alsatians completely lost in their calendars, it was exactly 440 years ago.