leap day

February 29 is a day added into a leap year of the Gregorian calendar.February 29 is also known as bissextile day. A year which has a February 29 is, by definition, a leap year. This date occurs only every four years, in years evenly divisible by 4, such as 1988, 1996, 2008 or 2024, with the exceptions in century years not divisible by 400, such as 1900.
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A leap year (or intercalary year) is a year containing one or more extra days (or, in case of lunisolar calendars, an extra month) in order to keep the calendar year synchronised with the astronomical or seasonal year. For example, February would have 29 days in a leap year instead of the usual 28. Seasons and astronomical events do not repeat at an exact number of full days, so a calendar which had the same number of days in each year would over time drift with respect to the event it was supposed to track. By occasionally inserting (or intercalating) an additional day or month into the year, the drift can be corrected. A year which is not a leap year is called a common year. In fact, the Earth takes slightly under 365 1/4 days to revolve around the Sun.
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Noun
1. the name of the day that is added during a leap year
(synonym) bissextile day, February 29
(hypernym) day
(part-holonym) February, Feb

leap-day /'li:pdei/
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