# Introduction

A leap year (in the Gregorian calendar) occurs:

- In every year that is evenly divisible by 4.
- Unless the year is evenly divisible by 100, in which case it's only a leap year if the year is also evenly divisible by 400.

Some examples:

- 1997 was not a leap year as it's not divisible by 4.
- 1900 was not a leap year as it's not divisible by 400.
- 2000 was a leap year!

~~~~exercism/note
For a delightful, four-minute explanation of the whole phenomenon of leap years, check out [this YouTube video](https://www.youtube.com/watch?v=xX96xng7sAE).
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