On what dates do the days and nights become equal all over the world?
"Equinox" means "equal night" in Latin. But even if the name suggests it and it’s widely accepted, it isn't entirely true that day and night are exactly the same on the equinox all over the world – only nearly.
What is an equinox?
On any other day of the year, the Earth's axis tilts a little away from or towards the Sun. But on the two equinoxes, the Earth's axis tilts neither away from nor towards the Sun, like the illustration shows. The equinoxes occur the moment the sun crosses the celestial equator – the imaginary line in the sky above the Earth’s equator. This happens in March and September every year.