February 30
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February 30 occurs in some calendars, unlike the Gregorian calendar, where February contains only 28 or 29 days.
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[edit] Swedish calendar
The Swedish realm (which included Finland at the time) planned to change from the Julian calendar to the Gregorian calendar beginning in 1704 by omitting the leap days for the next 40 years. Hence February 1704 had 28 days. This brought the Swedish calendar one day ahead of the Julian calendar but still ten days behind the Gregorian calendar. Contrary to the plan 1708 was still a leap year in Sweden.
To avoid confusion and further mistakes, the Julian calendar was restored when, in 1712, one extra leap day was added, thus giving that year a 30th of February. That date corresponded to February 29 in Julian and March 11 in Gregorian counting. The Swedish changeover to the Gregorian calendar was finally accomplished in 1753.
[edit] Soviet revolutionary calendar
In 1929 the Soviet Union introduced a revolutionary calendar in which every working month had 30 days and the remaining 5 or 6 days were 'monthless' holidays. In this calendar, there existed a 30th of February in the years 1930 and 1931; the revolutionary calendar was abandoned in 1931.
However, the Gregorian calendar continued to be used in the Soviet Union during this period. This is confirmed by consulting the successive dates in daily issues of Pravda, the official newspaper of the Communist Party, in which February had 28 days in 1930 and 1931, but had 29 days in 1932, which agrees with the rules of the Gregorian calendar, introduced in 1918.
[edit] Early Julian calendar
The 13th century scholar Sacrobosco claimed that in the Julian calendar February had 30 days in leap years between 45 BC and 8 BC, when Augustus shortened February to give the month of August named after him the same length as the month of July named after his adoptive uncle Julius Caesar. However, all other historical evidence relating to the Julian calendar during this period refutes Sacrobosco, including dual dates with the Alexandrian calendar. See Julian calendar: Month lengths.
[edit] Artificial calendars
Artificial calendars may also have thirty February dates. For example, in a climate model the statistics may be simplified by having twelve months of thirty days. The Hadley Centre General Circulation Model is an example.
[edit] References
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<ref>- The Oxford Companion to the Year. Bonnie Blackburn & Leofranc Holford-Strevens. Oxford University Press 1999. ISBN 0-19-214231-3. Pages 98-99.
