The legend goes that Leap Day William arises from the Mariana Trench every Leap Day to trade the candy for the tears of children. Not only that,.

DateSuMoTuWeThFrSaFebruary 29 in recent yearsFebruary 29, also known as leap day or leap year day, is a date added to most years that are by 4, such as,. A leap day is added in various (calendars based on the Earth's revolution around the ), including the standard in most of the world. (whose months are based on the ) instead add a leap or month.In the, years that are divisible by 100, but not by 400, do not contain a leap day. Thus, and did not contain a leap day; neither will,.

Conversely, and did and will. Years containing a leap day are called. Years not containing a leap day are called. February 29 is the 60th day of the Gregorian calendar in such a year, with 306 days remaining until the end of the year. In the, this day will only occur in years of the, and.A leap day is observed because the 's period of revolution around the takes approximately six hours longer than 365 whole days.

A leap day compensates for this lag, realigning the calendar with the 's position in the; otherwise, seasons would occur later than intended in the calendar year. Shining resonance refrain beatrice. The used in Christendom until the added a leap day every four years; but this rule adds too many days (roughly three every 400 years), making the equinoxes and solstices shift gradually to earlier dates. By the 16th century the vernal equinox had drifted to March 11, so the Gregorian calendar was introduced both to shift it back by omitting several days, and to reduce the number of leap years via the aforementioned century rule to keep the equinoxes more or less fixed and the date of consistently close to the.Leap days can present a particular problem in computing known as the when February 29 is not handled correctly in logic that accepts or manipulates dates. For example, this has happened with ATMs and Microsoft's cloud system. Main article:Although most modern calendar years have 365 days, a complete revolution around the Sun (one ) takes approximately 365 days, 5 hours, 48 minutes, and 46 seconds (or, for simplicity's sake, approximately 365 days and 6 hours, or 365.25 days).

An extra 23 hours, 15 minutes, and 4 seconds thus accumulates every four years (again, for simplicity's sake, approximately an extra 24 hours, or 1 day, every four years), requiring that an extra calendar day be added to align the calendar with the Sun's apparent position. Without the added day, in future years the would occur later in the calendar, eventually leading to confusion about when to undertake activities dependent on weather, or hours of daylight.Solar years are actually slightly shorter than 365 days and 6 hours (365.25 days), which had been known since the 2nd century BC when stated that it lasted 365 + 1 / 4 − 1 / 300 days, but this was ignored by and his astronomical adviser. The Gregorian calendar corrected this by adopting the length of the tropical year stated in three medieval sources, the, and the, truncated to two places, 365 14 / 60 33 / 3600 days or 365 + 1 / 4 − 3 / 400 days or 365.2425 days. The length of the tropical year in 2000 was 365.24217 mean solar days, Adding a calendar day every four years, therefore, results in an excess of around 44 minutes every four years, or about 3 days every 400 years. To compensate for this, three days are removed every 400 years.

The reform implements this adjustment by making an exception to the general rule that there is a leap year every four years. Instead, a year divisible by 100 is not a leap year unless that year is also. This means that the years 1600, 2000, and 2400 are leap years, while the years 1700, 1800, 1900, 2100, 2200, 2300, and 2500 are not leap years.Modern (Gregorian) calendar The Gregorian calendar repeats itself every 400 years, which is exactly 20,871 weeks including 97 leap days (146,097 days). Over this period, February 29 falls on Sunday, Tuesday, and Thursday 13 times; Friday and Saturday 14 times; and Monday and Wednesday 15 times. Except for a century mark that is not a multiple of 400, consecutive leap days fall in order Sunday, Friday, Wednesday, Monday, Saturday, Thursday, Tuesday, and repeats again.Early Roman calendar. Main article:The calendar of the Roman king had only 355 days (even though it was not a lunar calendar) which meant that it would quickly become unsynchronized with the solar year. An earlier Roman solution to this problem was to lengthen the calendar periodically by adding extra days to February, the last month of the year.

February consisted of two parts, each with an odd number of days. The first part ended with the on the 23rd, which was considered the end of the religious year, and the five remaining days formed the second part. To keep the calendar year roughly aligned with the solar year, called ('intercalary month'), was added from time to time between these two parts of February. The (usual) second part of February was incorporated in the intercalary month as its last five days, with no change either in their dates or the festivals observed on them. This followed naturally, because the days after the Ides (13th) of February (in an ordinary year) or the Ides of Intercalaris (in an intercalary year) both counted down to the Kalends of March (i.e.

They were known as 'the nth day before the Kalends of March'). The Nones (5th) and Ides of Intercalaris occupied their normal positions.The third-century writer says:When it was thought necessary to add (every two years) an intercalary month of 22 or 23 days, so that the civil year should correspond to the natural (solar) year, this intercalation was in preference made in February, between Terminalia 23rd and Regifugium 24th. Julian reform.