# Why do leap years exist?

Every four years we have a year with 366 days, called **leap** year, which was created in order to adjust the annual calendar to the Earth’s **translation** movement. In the leap year, the month of February has 29 days, instead of 28, as in other years.

**Whay does it happen?**

The year is the time the Earth takes to go around the sun: 365 days and about 6 hours – actually 5 hours 48 minutes and 46 seconds. These hours accumulate, and then every four years we have an extra day (24 hours).

Without this adjust, the **calendar** would be out of phase with the passing years, and some events would be changed, such us the season, for example. Astronomers have correted world clocks in one second at some some new year’s eve, which may dispense a revision of the calendar in the future.

**How calculate the leap year:**

So we can know if is a leap year, we just need to check if it does not end at 00 and if it is divisible by 4. The years ending at 00 will be leap years if their division by 400 is exact, that is, the result must be na **integer**.

· 1500 | · Non-leap |

· 1600 | · Leap |

· 1700 | · Non-leap |

· 1800 | · Non-leap |

· 1900 | · Non-leap |

· 2000 | · Leap |

· 2100 | · Non-leap |