What do you mean four years is a leap, a hundred years is not a leap, and 400 years is a leap?

Four-year leap: the year is a multiple of 4, which is a leap year;

One hundred years is not a leap year: it is a multiple of 100, not a leap year;

400 is a leap year: it is a multiple of 400, but it is a leap year.

The establishment of leap year is to make up for the time difference between the number of days in a year and the actual period of revolution of the earth caused by man-made calendar regulations. The year to make up for the time difference is leap year. Leap year * * * has 366 days (February is 1- 1 day, 29 days, 3 1 day, 30 days, 3 1 day, 3 1 day respectively).

Extended data

Calculation:

Calculation of leap month in lunar leap year, three-year leap, five-year leap, 19 leap; The lunar calendar basically takes 19 as a cycle, corresponding to the same time in the Gregorian calendar. For example, in the Gregorian calendar, May 27th, 2006, 5438+0, May 27th 1982 and May 27th 1963 are the fifth day of leap April.

The month of the leap month is inferred according to the laws of the lunar calendar, mainly according to the coincidence with the 24 solar terms of the lunar calendar;

The number of leap months in the lunar calendar is 29 or 30 days, just like normal months.

The so-called "leap" in the lunar calendar is just called leap year and leap month, and there are also leap years in the solar calendar.