Laura Laplaud 5:00 p.m., February 28, 2024

The year 2024 is a leap year and therefore has 366 days instead of 365. On the eve of February 29, a day which only returns every four years, let's return to the origin of leap years.

2012, 2016, 2020 and... 2024. Every four years, the year is a leap year and has 366 days instead of 365. If the month of February, the shortest of the year, has an extra day, namely February 29, as in 2024, the year is then a leap year.

But where do leap years come from?

## A request from Julius Caesar

To answer this question, let's go back to the times of ancient Rome.

We measure time from the movements of the Earth, its rotation on itself and its revolution around the sun.

At this time, astronomers calculate that the Earth takes 365.25 days to go around the sun.

Do you see the problem?

This extra quarter of a day had to be compensated and it was then that they decided to invent, at the request of Julius Caesar, the leap year.

From now on, every four years, a full day will be added to the calendar.

A way to reset the counters.

## February, last month of the year in the Roman calendar

But why add this day to the month of February?

Before the introduction of the Julian calendar in 45 BC.

BC, the Roman calendar was used.

It had 355 days, was organized in 12 months and began in "Martius", let's say March, and ended in "Februarius".

And as Julius Caesar's calendar required an extra day every four years, the Romans decided to add this day to the last month of the year, namely February.

The calendar then becomes solar: the length of the months is changed and the extra day is added between February 24.

Quite simply because the name leap day comes from the Latin "ante diem bis sextum Kalendas Martias", meaning sixth day before the kalends of March in French, that is to say February 24.

The additional day will finally be added at the end of February, on the 29th day, with the transition to the Gregorian calendar in 1582, the calendar which governs us today, explains the Institute of Celestial Mechanics and Calculation of Ephemeris (IMCCE) .

In France, 27,832 people have been born on February 29 since 1968, according to INSEE data.