There are 2 equinoxes every year – in September and March – when the sun shines directly on the equator and the length of day and night is nearly equal.
“Seasons are opposite on either side of the Equator, so the equinox in September is also known as the Autumnal (fall) equinox in the Northern Hemisphere.”
“The September equinox occurs the moment the Sun crosses the celestial equator – the imaginary line in the sky above Earth’s Equator – from north to south. This happens either on September 22, 23, or 24 every year.”
“On any other day of the year, either the southern hemisphere or the Northern Hemisphere tilts a little towards the Sun. But on the 2 equinoxes, the tilt of Earth’s axis is perpendicular to the Sun’s rays, like the illustrations show.”
“On the equinox, night and day are nearly exactly the same length – 12 hours – all over the world. This is the reason it’s called an “equinox”, derived from Latin, meaning “equal night”. However, even if this is widely accepted, it isn’t entirely true. In reality equinoxes don’t have exactly 12 hours of daylight.”