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February 30: Wikis


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February 30 occurs in some calendars, but not in the Gregorian calendar, where February contains only 28 or on a leap year (every 4 years) 29 days.


Swedish calendar

Swedish calendar February 1712

The Swedish Empire (which included Finland at the time) planned to change from the Julian calendar to the Gregorian calendar beginning in 1700 by omitting leap days for the next 40 years. Although the leap day was omitted in February 1700, the Great Northern War began later that year, diverting the attention of the Swedes from their calendar so they did not omit leap days on the next two occasions, causing 1704 and 1708 to remain leap years.

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 the Julian calendar and to March 11 in the Gregorian calendar. The Swedish changeover to the Gregorian calendar was finally accomplished in 1753 by omitting the last 11 days of February.

Soviet calendar

Although many sources state that 30-day months were used in the Soviet Union for part or all of the period 1929–1940, other sources as well as all surviving physical calendars from that period only show the irregular months of the Gregorian calendar, including a 28- or 29-day February, so the Soviet calendar never had a February 30.[1]

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 father Julius Caesar. However, all historical evidence refutes Sacrobosco, including dual dates with the Alexandrian calendar. (See Julian calendar.)

Artificial calendars

Artificial calendars may also have 30 days in February. For example, in a climate model the statistics may be simplified by having 12 months of 30 days. The Hadley Centre General Circulation Model is an example.


  1. ^ See Soviet calendar for a comprehensive list of sources, both for and against 30-day months.
  • The Oxford Companion to the Year. Bonnie Blackburn & Leofranc Holford-Strevens. Oxford University Press 1999. ISBN 0-19-214231-3. Pages 98–99.

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