A leap year

Do you know what a leap year? Here is one definition that I found on the internet.
First:
We say "leap year" because each date on the calendar jumps ahead two days of the week instead of one.

Leap year:
A year containing an extra day. It has 366 days instead of the normal 365 days.

Leap years occur every 4 years. 2020 is a leap year and so is 2024.

However, every 100 years special rules apply. For example, 1900 was not a leap year, but 2000 was.

The extra day is added in February, which has 29 days instead of the normal 28 days.

That is why I believe February, not December, is the end of the year. February is the only month with 28 days. All the other months have 30 or 31 days. And, we add the extra day to February.
Do you follow me?