Because the Earth rotates about 365.242375 times a year. Years consisting of 12 months have between 353 and 355 days. In a k`sidra (“ok”) year of 354 days, the months alternate 30 and 29 days. In a year of pursuit (“missing”), the month of Kislev is reduced to 29 days. In a malei (“filled”) year, the month of Marcheshvan is increased to 30 days. The 13-month years follow the same pattern, with the addition of the 30-day Adar Alef, which gives them between 383 and 385 days. To determine if a year is a leap year, the tradition in Finland is that if a man rejects a woman`s request on a leap day, he should buy her the fabrics for a skirt.  The Civil Code of Taiwan since October 10, 1929, implies that the legal birthday of a jumper in the ordinary years of the 28th. February is: So every 100 years we don`t have a leap year, and that brings us 365.24 days a year (1 day less in 100 years = -0.01 days a year). Closer, but still not accurate enough! Leap years are a way to make sure our calendar is on track. There are about 365.24 days in a year, which means that once every 4 years we have to add 1 extra day, and a year with 1 extra day is called a leap year. We need to do this to make sure we don`t fall several hours behind every year. Calculating leap years is easy, but there are a few special rules you need to keep in mind when doing your calculations.
If you`d rather look at a calendar than calculate, then this is also an option. Technically, a jump will have fewer birthday anniversaries than its age in years. This phenomenon is exploited when a person claims to be only a quarter of his real age by counting only his leap year anniversaries: in Gilbert and Sullivan`s comic opera The Pirates of Penzance of 1879, the apprentice pirate Frédéric discovers that he must serve the pirates until his 21st birthday (that is, when he will be 88 years old, since 1900 was not a leap year) and not before the age of 21. The Gregorian calendar is closely based on the Julian calendar, which was introduced by Julius Caesar in 45 BC. J.-C. to fix the Roman calendar (including the addition of a few more months). The Julian calendar included a 12-month year with 365 days, with an intercalary day inserted every four years at the end of February to get an average year of 365.25 days. But because the length of the solar year is actually 365.242216 days, the Julian year was too long by 0.0078 days (11 minutes 14 seconds). If you were born in a leap year, can you get your driver`s license as early as February 28? Well, each state decides whether February 28 or March 1 is the day you`re eligible to get your license. However, most states consider March 1 to be the official day. For example, the Michigan Vehicle Code states that people born on February 29 “shall be considered to be born on March 1.” Another fun fact: leap year babies still have their driver`s license even though they are officially four years old (16)! However, there are no rules on when you have a party, so it`s really a free game during the day in February or March to celebrate a leap year anniversary. Tip: Remember that sometimes there is no leap year for 8 years, as there are just under 6 overtime hours each year – 5 hours, 48 minutes and 46 seconds to be exact.
 X Research source Therefore, it is useful to perform calculations instead of relying on a leap year every 4 years. It may not seem like much, but over the centuries it has added up. Until the 16th century, the spring equinox fell around March 11 instead of March 21. In 1582, Pope Gregory XIII adjusted the calendar by advancing the date by 11 days and introducing the exception to the rule for leap years. This new rule, according to which a centenary year is a leap year only if it is divisible by 400, is the only feature that distinguishes the Gregorian calendar from the Julian calendar. . So something needs to be done to “catch up” the additional 0.242375 days per year. The extra leap day adjusts this drift, but it`s not a perfect match: adding a leap day every four years overcompensates for each leap year by a few extra seconds and adds about three extra days every 10,000 years. Leap years keep our calendars under control! Let`s explain why leap years are necessary and share some of the fun folklore that surrounds them. www.mathworks.com/matlabcentral/answers/120572-if-else-condition-to-determine-if-a-year-is-a-leap-year#comment_200474 The Chinese calendar is lunisolar, so a leap year has an extra month, which is often called the embolic month after the Greek word for this. In the Chinese calendar, leap month is added according to a rule that ensures that month 11 is always the month that contains the northern winter solstice. The infill month assumes the same number as the previous month; For example, if it follows the second month (二月), then it is simply called “Second Leap Month”, that is, simplified Chinese: 闰二月; Traditional Chinese: 閏二月; Pinyin: Rùn`èryuè.
In the Gregorian calendar, a normal year consists of 365 days. Since the actual duration of a sidereal year (the time it takes for the Earth to once orbit the Sun) is actually 365.2425 days, a “leap year” of 366 days is used once every four years to eliminate the error caused by three normal (but short) years. Any year evenly divisible by 4 is a leap year: for example, 1988, 1992 and 1996 are leap years. Leap years can be a problem in data processing known as leap year bugs when a year is not properly identified as a leap year, or when the 29th. February in the logic that accepts or manipulates data is not processed correctly. The medieval church continued the Roman practice, which can be illustrated, for example, by the feast of St. Matthias, celebrated both in the municipality and in the leap year on the sixth day before the March calendars. The February calendar in the Book of Common Prayer of 1549 shows the position in a normal year where the feast of St. Matthias is the sixth day before the Calendars of March, which is next to February 24. The position in a leap year is not shown in the Church of England`s Book of Common Prayer of 1549, but the previous insertion of the second sixth day meant that the feast of St. Matthias fell on February 25 in leap years. This practice ended in England some time after the secession of Henry VIII from Rome, especially in the 1662 edition of the Book of Common Prayer.
 The counting of consecutive days completely replaced the Roman system. The feast of St. Matthias is without exception on February 24 and the leap day is shown at the end of February.  [a] A “leap day” is the additional day of the leap year: February 29. In other words, a centenary year can only be a leap year if it is divisible by 400. So 1700, 1800 and 1900 were not leap years, but 1600, 2000 and 2400 are leap years. In Ireland and the United Kingdom, it is traditional for women to only be able to propose marriage in leap years. Although it has been claimed that the tradition was initiated by St Patrick or Brigid of Kildare in 5th century Ireland, this is doubtful as the tradition was not observed until the 19th century.  Apparently, a law passed by Queen Margaret of Scotland in 1288 (then five years old and living in Norway) required fines to be imposed if a marriage proposal was rejected by the man; The compensation was considered a pair of leather gloves, a single rose, £1 and a kiss.
 In some places, the tradition of limiting female proposals to the modern leap day on February 29 or the medieval leap day (leap) on February 24 has been strengthened. I am a jumper, I officially had 9 real birthdays, my nephew of 8 years can not put his head around us because he is the same age this year because I am an adult (supposedly), I celebrate on March 1st when there is no 29. My parents were told we couldn`t celebrate the 28th because I wasn`t there that day. The Julian calendar was created in 45 BC. J.-C. Introduced by order of Julius Caesar, and the original intention was to make each fourth year a leap year, but this was not done correctly. Augustus ordered to omit a few leap years to solve the problem, and around 8 AD, leap years were observed every four years, and customs were consistent throughout modern times. .