Every year at Stonehenge, the autumn equinox is celebrated.
The autumn equinox occurs around September 22. The stones are opened as soon as it gets light enough to be safe, about 20 minutes before sunrise.
After the equinox, the days will get shorter and the nights will get longer. The shortest day is around 21 December when the days will start to get longer again.
At the moment of the autumnal equinox, our planet reaches the turning point in its orbit where neither of the poles are tilted towards the sun. The sun is exactly above the equator between the Northern and Southern Hemisphere. In the Northern Hemisphere it marks the first day of autumn, according to the astronomical calendar.
The word ‘equinox’ means ‘equal night’.