The leap year of 2020 is about to pass - four years a leap, a hundred years without a leap, four hundred years again

Xiaoming's birthday is only once in 4 years, what day is his birthday?

This is the rotten intellectual sharp turn problem, and everyone knows the answer, it is February 29.

The problem that everyone is familiar with is actually a geographical problem, that is, the leap year.

Now the primary school Olympiad problems are often used to make articles in leap years, changing the pattern can make a lot of problem types, and the math teacher will let students remember the "four years a leap, a hundred years not leap, four hundred years and then leap" mantra, which is conducive to doing the problem.

Today we will talk about geography and how this recipe came about.

The last time the earth was rotated was about 365 days, the accurate number should be 365 days, 5 hours, 48 minutes and 46 seconds, which is converted into days, which is 365.24219 days.

Since about 6 hours more per year is not easy to calculate, it is called a flat year with 365 days as a year.

About 6 hours more in a year, 24 hours more in 4 years, that is, 1 day. That fourth year adds one day, and the whole year is 366 days, called a leap year.

This day adds up to February, which is February 29.

That's a leap every four years.

Due to the extra 0.24219 days per year, four more days out of 0.96876 days, in fact, less than one day, more than 0.03124 days. On average, in each year, it is 0.00781 days per year. Then 400 years, 3.124 more days, about 3 days.

Therefore, every 400 years, 3 days are subtracted, that is, 3 leap years.

Therefore, the international rule is that when the year is a full hundred, it must be a multiple of 400 to be a leap year. Even if the year is a multiple of 4, but not a multiple of 400, it cannot be a leap year, so that 400 years are exactly 3 days minus.

This is a hundred years without leaps, and four hundred years again.

Let's take another example for everyone to understand.

2000 is a leap year, and this year 2020 is a multiple of 4, which is also a leap year. 2100, 2200, 2300 are not leap years. 2400 is a leap year.

There are so many surprises in 2020! This leap year is about to pass, what is the next leap year?

In 2024.