Important events in September/ The beginning of autumn or the equinox: what is it exactly?

HIBAPRESS-RABAT-JM

This is the time when the length of the day is equal to that of the night, 12 hours each. In fact, the word equinox is formed from two Latin terms: “aequus” which means “equal” and “nox, noctis” which means “night”. Astronomically, this is when the sun is exactly vertical to the equator. It is also the day when the sun will rise due east and set due west.

There are two equinoxes each year. One between March 19 and 21, when we transition from winter to spring in the Northern Hemisphere, and the second between September 21 and 24, when we transition from summer to fall.

Because a year lasts 365 days but the Earth takes exactly 365 days, 5 hours and 48 minutes to make a complete rotation of the sun. It is this shift that changes the dates and times of the equinox. It is to catch up with this shift that there is an extra day every four years, in leap years (the next one will be in 2024). And that also shifts the equinox.

Ultimately, the equinox falls between September 21 and 24 depending on the year.

For the years 2024 and 2025, the autumn equinox is predicted to occur on September 22, as was the case in 2020 and 2021.