While in the meteorological calendar, the start of autumn falls on 1 September, the astronomical calendar follows the solstices and equinoxes. In this interpretation of the seasons, the autumn equinox signals the arrival of autumn.
With the nights drawing in, the clocks change not long after the autumn equinox – so summer is very much in the rear-view mirror.
What is the autumn equinox?
The word ‘equinox’ comes from the Latin term for ‘equal night’. It describes the two days that occur each year – autumn equinox and spring equinox – when night and day are of equal length.
The autumn equinox falls when the Earth’s axis is tilted neither toward nor away from the Sun, resulting in equal night and day. The Sun appears to be directly over the Earth’s equator.
This begins the period in which the top half of the Earth receives less sunlight every day, culminating in the winter solstice in December (the shortest day). The reverse takes place for the spring equinox each year: the globe gradually receives more sunlight each day, heading towards the summer solstice (longest day) in June.
When is the autumn equinox?
In 2025, the autumn equinox falls on Monday 22 September. This is the schedule for the autumn equinox for the coming years:
2026: Wednesday 23 September
2027: Thursday 23 September
2028: Friday 22 September
2029: Saturday 22 September
2030: Monday 23 September
More seasonal stories
- How the UK's seasons are changing and the impact on the countryside
- Best autumn walks in the UK: discover stunning trails through golden forests and scenic countryside
- Britain's most spectacular autumn arboretums
- Best places in the UK to see autumn colours
Top image: Stonehenge at the autumn equinox (credit: Getty Images)
