1. Leap years are divided into ordinary leap years and century leap years: those in which the Gregorian calendar year is a multiple of 4 are ordinary leap years; The Gregorian calendar year is a whole hundred, and it must be a multiple of 400 to be considered as a leap year (century leap year).

2.2000 can be divisible by 400, and 2000÷400=5. The year 2000 is a leap year in this century.

3. Ordinary leap year from 2000 to 2020, 2004 ÷ 4 = 501; 2008÷4=502; 20 12÷4=503; 20 16÷4=504; 2020÷4=505, which means that 2004, 2008, 20 12, 20 16 and 2020 are all common leap years.

4. There are six leap years, namely: 2000, 2004, 2008, 20 12, 20 16, 2020.

Extended data:

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).

The Gregorian calendar has only leap years and peace years, with 365 days in a normal year and 366 days in a leap year (one more day in February); There may also be leap months in a normal year (for example, 20 17 is a normal year, and there are leap months and leap months in the lunar calendar).

Baidu encyclopedia-leap year