// BBC UK NEWS — CRONACA
Autumn equinox 2026: When is it and what happens?
Astronomical autumn begins this week, with the autumn equinox taking place in the early hours of Wednesday.
The equinox will occur at 01:06 BST on 23 September, according to Royal Museums Greenwich.
It is a precise moment in time when the Sun crosses the celestial equator and neither hemisphere is tilted towards or away from the Sun, meaning day and night are roughly equal in length across the world.
And while the equinox itself cannot be seen, the day has cultural and spiritual significance for some people. Gatherings take place at sites including Stonehenge, where people come together to mark the occasion and watch the Sun rise.
Many people, including druids and pagans, gather at Stonehenge to take part in a autumn equinox celebration
The word "equinox" comes from Latin and means equal night.
At the equinox, the daylight measurement is taken from the point when the centre of the Sun is at the horizon, and is 12 hours sunrise to sunset and 12 hours sunset to sunrise.
However, it is the top edge of the Sun which is visible first at sunrise and last at sunset.
Because of light refraction - light being bent by the atmosphere - there is still light for a time when the Sun is not directly visible. This adds extra time to daylight hours.
In autumn, this means that the time when day and night are actually equal happens after the equinox.