Seasonal · countdown to autumn
Fall Clock
Drifting leaves in warm autumn colours, with a live countdown to the September equinox and the current time. Counts to the start of astronomical autumn in the northern hemisphere.
Until autumn begins
—
Press F for full screen. Motion pauses automatically if your system asks for reduced motion.
When autumn starts
Two Different Answers, Both Used
The Astronomical Answer
Autumn begins at the September equinox, when the sun crosses the celestial equator and day and night are close to equal length. That falls on 22 or 23 September in most years. This countdown uses 22 September as its target.
The Meteorological Answer
Weather services define autumn as the whole of September, October and November, starting on 1 September. Splitting the year into three-month blocks makes climate records far easier to compare, which is why forecasters use it.
Why They Disagree
The astronomical seasons follow the Earth's tilt, which does not divide neatly into calendar months. The meteorological ones follow the calendar. Neither is wrong; they answer slightly different questions.
The Southern Hemisphere
Everything is inverted below the equator. The September equinox marks the start of spring in Australia, South Africa and South America, and autumn there begins around 20 March.
Under the hood
How This Scene Is Built
The leaves fall on individual paths with a slow tumble, in six colours drawn from the usual autumn palette. Each one has its own duration and delay, which is what stops the scene looking like a repeating loop.
For the exact equinox moment rather than the calendar day — it varies by a few hours from year to year, and can land on the 22nd or 23rd depending on your time zone — the custom countdown lets you enter a precise date and time.
Answers
Fall Background Questions
Which date is the countdown using?
22 September, which is the September equinox in most years. The exact astronomical moment shifts by a few hours annually and can fall on the 23rd in some time zones.
Why does autumn have two start dates?
Astronomers date it from the equinox; meteorologists date it from 1 September so that seasons align with whole months and climate statistics compare cleanly. Both definitions are in everyday use.
I am in the southern hemisphere — is this wrong for me?
The countdown targets the September equinox, which is the start of spring where you are. For southern autumn, set 20 March on the custom countdown page.
Why do leaves change colour?
As days shorten, trees stop producing chlorophyll and reclaim nutrients from their leaves. The green fades, revealing yellow and orange pigments that were present all along, while reds are newly made in the leaf as it declines.
Can I slow the leaves down?
They already fall at varied speeds. To stop them entirely, press pause motion.