February 30 Has Happened Twice
Twice in history have countries had to arrange for February 30. In one case, the day occurred as part of the conversion between the Julian and Gregorian calendars; Sweden had to add the day in
1712 because it made the wrong years leap years during its initial attempts to convert in 1700. This messed up the country’s calendar so badly that everyone had to return to the Julian calendar temporarily. In 1712, the country changed the official Gregorian calendar and added two leap days- February 29 and 30- to catch up.
The second time was in the Soviet Union between 1930 and 1931. The Soviet Revolutionary calendar, introduced in 1929, created six 5-day weeks per month, with five to six holidays at the end of the year. That gave February 30 days, but the country continued to observe the Gregorian calendar in everyday life, and later the 5-day week was abandoned.