Sweden's Calendar Chaos: February 30th Exists

Sweden once had a February 30th — the only country in recorded history to add that nonexistent date to its calendar — and the reason involves one of the most spectacularly botched calendar reforms ever attempted. The story begins with a sensible idea, detours through forty years of confusion, and ends with a date that should not exist appearing on the Swedish calendar in 1712. The problem was the gap between the Julian and Gregorian calendars. By 1700, the Julian calendar, which most Protestant countries still used, had drifted ten days behind the Gregorian calendar adopted by Catholic nations in 1582. Most countries that switched simply deleted the extra days overnight — Britain, for instance, jumped from September 2 to September 14 in 1752, prompting (possibly apocryphal) protests demanding "Give us our eleven days!" Sweden chose a different approach: it would gradually shift to the Gregorian calendar by skipping all leap days between 1700 and 1740, eliminating one extra day per cycle until the calendars aligned. The plan went wrong almost immediately. Sweden successfully skipped the leap day in 1700, putting it one day ahead of the Julian calendar but still nine days behind the Gregorian one. Then the Great Northern War erupted, Karl XII was consumed with fighting Russia, and everyone forgot about the calendar reform. Leap days were observed normally in 1704 and 1708, meaning Sweden was now on a calendar shared by no other country on Earth — one day off from Julian and nine days off from Gregorian. In 1712, the Swedish government gave up on the gradual approach and decided to return to the Julian calendar by adding the day it had previously skipped. Since 1712 was already a leap year, Sweden added an extra day after February 29, creating February 30, 1712 — a date that has appeared on no calendar before or since. Sweden eventually adopted the Gregorian calendar properly in 1753 by the British method, jumping from February 17 to March 1. The entire episode lasted fifty-three years and accomplished nothing except producing one of history's most endearing bureaucratic absurdities.