Why do we have a leap year?

We have 365 days in a normal year. But, every four years, we have a leap year which is one more day of February. But why do we have a leap year? A year is how long the earth takes to rotate around the sun. But, it's not like every four years the earth takes one more day than the last three years.

Now I know why they make a leap year. They make a leap year because every year is is not 365 days, but 365.24219 days which is rounded to 365 ¼ days. But, 365.24219 days is a little bit less than 365 ¼ days and over time, it adds up. Therefore, only in centuries years if it is divisible by 400, it is a leap year, but if it is not divisible by 400, it is not a leap year.

This is why we have a leap year and what the problem is if we don’t.
For more information, visit http://www.cnn.com/2016/02/29/tech/why-do-we-have-leap-year/index.html