You can use a formula: jump in four years, not jump in a hundred years, and jump again in four hundred years.
You can use the simplest one: leap years can be divisible by 4. (For example, 2004 is a leap year, and 200 1 is not. )
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The usual explanation is that there are many days, hours and minutes in a year, so it is unnecessary to take the integer 365. After the cumulative number reaches 24 hours a day, the year with one more day is a leap year. This explanation just tells everyone how to calculate, which is artificially set.
The most fundamental reason is that the cycle of the earth's orbit around the sun is 365 days, 5 hours, 48 minutes and 46 seconds (365 days +09 days), which is the tropic of cancer. The Gregorian calendar has an average of only 365 days a year, which is about 0.2422 days shorter than the tropical year, and the remaining time is about one day every four years. So 1 day is added at the end of February of the fourth year, making the calendar year of that year 366 days, and this year is a leap year.
The current Gregorian calendar has 97 leap years every 400 years. According to a leap year every four years, it will count as 0.0078 days per year on average, so after 400 years, it will count as 3 days. So every 400 years, three leap years will be reduced.
This is what is usually said: jump in four years, not jump in a hundred years, and jump again in four hundred years. For example, 2000 is a leap year, and 2 100 is a normal year.
Baidu encyclopedia-leap year