Determination of leap year in Gregorian calendar

The common sense is that a leap year is four years, and a year that is divisible by four is a leap year, but this is not necessarily the case. Which years are leap years? How to judge leap year?

In the Gregorian calendar year, the year with leap days is called leap year, with 365 days in general and 366 days in leap year. Because the earth's orbit around the sun is 365 days, 5 hours, 48 minutes and 46 seconds (365.24219 days), that is, the year is 365 days in the Gregorian calendar. The remaining time is about four years, and it is added to and fixed in February, so there are 365 days in a normal year, 28 days in February, 366 days in a leap year and 29 days in February. There are 97 leap years in every 4 years.

the usual calculation method of leap year: the number of years in the AD calendar year can be divisible by 4, which is a leap year; However, years divisible by 4 are not necessarily leap years, such as 17 and 19, which are not leap years. In the year of the turn of the century, the year that is divisible by 1 but not by 4 is the average year; A leap year is exactly divisible by 1 or 4. For example, the year 2 is a leap year, while the years 1 and 3 are not. Here is a leap year calculation formula, you can have a look if you are interested.