Days Until Fall
Count the days until fall begins. Choose astronomical fall (the September equinox, September 22 or 23 in US time zones) or meteorological fall (September 1), and count from today by leaving the date blank - or from any date you pick.
Meteorologists start fall on September 1 to keep seasons in tidy 3-month blocks; astronomers wait for the equinox, about three weeks later - NOAA.
Two starts of fall
Astronomical fall begins at the September equinox - the instant the Sun crosses the celestial equator heading south, which lands on September 22 or 23 in US time zones. Because the exact moment shifts by almost 6 hours a year (and leap years yank it back), the calendar date wobbles: September 22 in 2026, September 23 in 2027.
Meteorological fall simply runs September 1 through November 30. Weather agencies like NOAA prefer whole months because temperature statistics group naturally that way, so 'first day of fall' in a climate report is about three weeks earlier than the equinox everyone else quotes.
Equinox timing details
The equinox is a single global instant, so its calendar date depends on your time zone: the 2026 equinox falls late on September 22 in US zones but after midnight UTC, already September 23 in Europe. This calculator uses the US (Eastern Time) date. Despite the name - equal night - day and night are not exactly 12 hours at the equinox; refraction and the Sun's disk size push the true 12-hour split a few days later.
How it’s calculated
Astronomical mode counts to the September equinox date in US Eastern Time from a built-in table for 2025-2031 (Sep 22 in 2025, 2026, 2028, 2029, 2030; Sep 23 in 2027 and 2031, per USNO/NASA equinox tables); outside the table September 22 is assumed and flagged. Meteorological mode counts to September 1 (NOAA convention). Days = round((start of fall − start date) / 86,400,000 ms), dates anchored at noon; if fall already began this year, the count targets next year.
Equinox dates are the US Eastern Time calendar dates - in UTC or Asia/Europe time zones the equinox can fall one calendar day later.
When fall starts, 2026-2031
| Year | Astronomical (equinox, US ET) | Meteorological |
|---|---|---|
| 2026 | September 22 | September 1 |
| 2027 | September 23 | September 1 |
| 2028 | September 22 | September 1 |
| 2029 | September 22 | September 1 |
| 2030 | September 22 | September 1 |
| 2031 | September 23 | September 1 |
September equinox dates (US Eastern Time) from USNO/NASA published equinox tables; meteorological convention per NOAA.
Common mistakes
- Assuming fall always starts September 21 - in current decades the US equinox lands on the 22nd or 23rd; September 21 won't happen again until late this century.
- Mixing definitions mid-plan: a pumpkin-patch opening 'first day of fall' may mean September 1 (meteorological) while an almanac means the equinox, three weeks later.
- Ignoring time zones - the same equinox instant can be September 22 in the US and September 23 in Europe, so overseas sources may disagree by a day.
- Counting to the equinox of the current year after it has passed; from October the correct target is next year's equinox, 11+ months out.
Frequently asked questions
How many days until fall?
Days = (start of fall − today) / 86,400,000 milliseconds. With astronomical fall, the target is the next September equinox (September 22, 2026 in US time zones); with meteorological fall it is the next September 1.
Why are there two first days of fall?
Astronomers define seasons by the Sun's position - equinoxes and solstices - while meteorologists use fixed month blocks (September-November) so climate statistics compare cleanly year to year. Both are legitimate; they differ by about three weeks.
Is the equinox always the same date?
No. The equinox instant arrives about 5 hours 49 minutes later each year, then jumps back a day after a leap year, so the US date alternates between September 22 and 23 in this era.
Are day and night exactly equal on the equinox?
Not quite. Atmospheric refraction and measuring sunrise from the Sun's upper edge give slightly more than 12 hours of daylight on the equinox; the true 12-hour split (equilux) comes a few days after in fall.
When does fall end?
Astronomical fall runs to the December solstice (December 21 or 22); meteorological fall ends November 30. Whichever definition you start with, use the same one for the end date.