What Autumn Equinox is

The moment the sun crosses the celestial equator heading south, when day and night are near equal and the northern hemisphere tips towards winter.

It is the start of astronomical autumn in the north and spring in the south.

Why this date does not move

The countdown at the top of this page is live, and the date beneath it is the next occurrence. This is a fixed date: it falls on the same day of the month every year, so only the weekday changes.

The date follows a fixed calendar rule, so it can be computed years ahead. Where a country observes this as a public holiday, the official government calendar remains the authority for whether the day off is moved when it falls on a weekend.

What is coming up next

Once this date passes, the countdown moves on according to the recurrence rule described above. Calculated lunar dates remain estimates until the relevant calendar or local authority confirms them. See the full list of upcoming events, or use the countdown timer for a duration of your own.