Countdown to
The First Day of Fall
Day and night in balance, and the year turns
Today is the First Day of Fall.
325 days until the First Day of Fall, on Thursday, September 23, 2027.
The First Day of Fall is Thursday, September 23, 2027. Happens the September (autumn) equinox (computed astronomically, in UT).
The first day of fall is the September equinox, when the Northern Hemisphere tips back toward winter and day and night fall into near-perfect balance. Around September 22 or 23 the Sun crosses the celestial equator heading south, daylight and darkness split almost evenly, and astronomical autumn begins — the slow slide toward shorter days, cooler air, and the harvest.
It is a hinge rather than a peak: the heat of late summer lingers for weeks, but the light has already turned a corner. From the equinox on, nights grow longer than days across the whole hemisphere.
How we get this date. The countdown is pinned to the exact instant of the September equinox, computed from Jean Meeus’s Astronomical Algorithms (Ch. 27) and given in Universal Time. Autumn officially begins the moment the Sun’s center crosses the celestial equator going south. Because a year runs about a quarter-day past 365, that instant drifts roughly six hours later each common year and snaps back at each leap day, so the first day of fall almost always lands on September 22 or 23.
Forecasters keep a different calendar. Meteorological autumn starts on September 1, bundling September, October, and November into a climate season that lines up with the cooling temperature cycle — so meteorological fall opens about three weeks ahead of the astronomical first day.
The name promises equal day and night, but the balance is approximate. Because the atmosphere bends sunlight and we measure the day from the Sun’s upper edge, daytime runs a few minutes longer, and the true 12-hour day — the equilux — arrives a few days after the equinox.
A timezone note. The equinox is a single moment in Universal Time, so the first day of fall can differ by a calendar day around the world. In 2026, for example, the Sun crossed the equator at about 00:05 UT on September 23 — already the 23rd in Europe, Africa, Asia and Australia, but still the evening of September 22 across the Americas. The instant is shared; the date on the wall is not.
Culturally the first day of fall means harvest and homecoming — apple and pumpkin picking, the Harvest Moon riding low and bright near the equinox, Mabon gatherings of thanks and balance, and Japan’s Shubun no Hi holiday for tending ancestral graves. However you mark it, it is the calendar’s turn toward crisp air, early evenings, and the year’s long wind-down.
🍂 Fun facts about the First Day of Fall
- Meteorological autumn begins on September 1, so forecasters count fall as starting about three weeks before the astronomical first day set by the equinox.
- On the first day of fall the Sun rises almost due east and sets almost due west for nearly everyone on Earth — one of only two dates a year that happens.
- The name 'equinox' means 'equal night,' but daytime actually runs a few minutes longer; the true 12-hour day, the equilux, comes a few days later.
- The full moon nearest the September equinox is the Harvest Moon, whose bright, early-rising light once let farmers work well past sunset.
- In the Southern Hemisphere the September equinox is the first day of spring, not fall.
Upcoming First Day of Fall dates
| Date | Days away |
|---|---|
| 325 days | |
| 690 days | |
| 1,055 days | |
| 1,420 days | |
| 1,786 days |
How people mark the First Day of Fall
- Apple and pumpkin picking
- Harvest festivals and Mabon gatherings
- Watching the Harvest Moon rise
- Back-to-routine and cozy home decorating
- Tending ancestral graves in Japan during Higan
Frequently asked
When is the first day of fall?
In the Northern Hemisphere it is the September equinox, which falls around September 22 or 23 each year. It marks the moment the Sun crosses the celestial equator heading south and day and night fall into near balance.
How is the date calculated?
The countdown is pinned to the exact instant of the September equinox, computed from Jean Meeus's Astronomical Algorithms (Ch. 27) and given in Universal Time — the moment the Sun's center crosses the celestial equator heading south.
Is the first day of fall the same as meteorological fall?
No. Meteorological autumn always begins September 1 so climate records split into three-month seasons. The astronomical first day, tied to the equinox, arrives roughly three weeks later.
Are day and night exactly equal on the first day of fall?
Almost, but not quite. Atmospheric refraction and the Sun's width make daytime a few minutes longer, so the true 12-hour day — the equilux — comes a few days after the equinox.