February 30 was a real date
Historical records show that February 30 was a real date at least twice in history. Sweden added the date to its 1712 calendar following an earlier calendar error; the Soviet Union observed February 30 in 1930 and 1931 in an attempt to cut seven-day weeks into five-day weeks and to introduce 30-day months for every working month.
Sweden’s 30 days of February
In 1700 Sweden, which included Finland at the time, planned to convert from the Julian calendar to the Gregorian calendar. Therefore 1700, which should have been a leap year in the Julian calendar, was not a leap year in Sweden. However, 1704 and 1708 became leap years by error. This left Sweden out of synchronization with both the Julian and the Gregorian calendars, so the country reverted back to the Julian calendar.
February 30, 1712, came into existence in Sweden when the Julian calendar was restored and 2 leap days were added that year. Sweden’s final conversion to the Gregorian calendar occurred in 1753, when an 11-day correction was applied so that February 17 was succeeded by March 1 that year. Not everyone was pleased with the calendar reform. Some people believed it stole 11 days of their lives.
The Soviet revolutionary calendar
February 30 existed from 1930-1931 after the Soviet Union introduced a revolutionary calendar in 1929. This calendar featured five-day weeks, 30-day months for every working month, and the remaining five or six days were “monthless” holidays. The abolition of the seven-day week in favor of a five-day week was intended to improve industrial efficiency by avoiding the regular interruption of a non-working day.
However, the Gregorian calendar continued to be used in the Soviet Union during this period. This is confirmed by successive dates found in daily issues of Pravda, the official newspaper of the Communist Party, in which February had 28 days in 1930 and 1931, in accordance with the Gregorian calendar. The Soviet revolutionary calendar was discarded as it was difficult to eliminate the Sunday rest tradition. The original seven-day week was restored in 1940.