Day 366, February 29th. Divide the year number by four and you will get one, two and three. March 365, February 28. In 2000, it was difficult to calculate. The divisor is 400, and the rest are leap years. Leap in four years, leap in one hundred years, leap in four hundred years. It is easy to judge a normal year and a leap year. If a unit is odd (singular), there is no need to divide it. At first glance, there is a remainder. The last two digits of a general year and the first 20 digits of a hundred years are divided by 4 respectively, and the remainder is a normal year and a clean leap year.
Leap year is a term in the Gregorian calendar. A normal year (a year not divisible by 100) is a leap year divisible by 4. (For example, 2004 is a leap year, 1999 is not); Century year (the year divisible by 100) is a leap year divisible by 400. (For example, 2000 is a leap year, 1900 is not).
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).