The first day of autumn in 2025 falls on Monday, September 22, at precisely 2:19 p.m. EDT (18:19 UTC). This is the moment of the autumnal equinox, when the Sun’s center crosses Earth’s equator heading south, and day and night are nearly—but not exactly—equal.
Table of Key Times for the Autumnal Equinox (2025)
| Time Zone / Location | Local Date | Local Time | Notes |
|---|---|---|---|
| Eastern Daylight Time (EDT, USA) | September 22, 2025 | 2:19 p.m. | “First day of autumn” officially begins at this moment for many in the U.S. |
| Coordinated Universal Time (UTC) | September 22, 2025 | 18:19 | Universal reference time for astronomical events. |
| British Summer Time (BST, UK) | September 22, 2025 | 7:19-7:20 p.m. | Equivalent local time in London etc. |
What Is the “First Day of Autumn”?
To avoid confusion, here are the two main ways people define the first day of autumn, especially in meteorology and astronomy:
- Astronomical definition: when the autumnal equinox happens. This is the moment the Sun crosses the celestial equator going south. It signals the official beginning of autumn in the Northern Hemisphere.
- Meteorological definition: falls on September 1 in many places—this is for statistical or temperature-based seasons rather than astronomical alignment.
In this article, “first day of autumn” refers to the astronomical autumn, as per the equinox.
Why the Autumnal Equinox Matters
Understanding what happens on the equinox gives more depth than simply noting a date. Here are some of the key phenomena and meanings:
- Equal day and night (almost): The term equinox is from Latin (aequus = equal, nox = night). At equinox, day and night are nearly of the same length globally. But due to atmospheric refraction and how sunrise & sunset are measured, daylight is often a few minutes longer.
- Sun crossing the celestial equator: The Sun shifts from above (north of) the equator to below it (southward).
- Shift in seasons: In the Northern Hemisphere, the days start getting shorter, the angle of sunlight lowers, nights get longer. The Southern Hemisphere experiences the reverse—transition toward spring.
How the First Day of Autumn Affects Life & Nature
Autumn isn’t just calendar stuff. The equinox ripples through nature, culture, climate, and even how we feel. Here are some major impacts:
| Domain | What Happens Around Autumn Equinox |
|---|---|
| Nature & ecology | Leaves begin changing color, many plants slow photosynthesis, migrations begin (birds, insects). Twilight shifts; shadows lengthen. |
| Climate / weather | Cooling trend in many temperate zones; daylight hours decline noticeably; nights colder than days. |
| Culture & tradition | Harvest festivals, rituals of balance and transition, ceremonies in many societies. |
| Astronomy & observation | Better skies for observing constellations that rise in autumn, changes in sun path; equinox helps calibrate certain celestial measurements. |
Common Misconceptions About the First Day of Autumn
It’s easy to get things slightly wrong. Clarifying these helps ensure accuracy, especially for SEO content that aims to serve user intention.
- “Day and night are exactly equal” – Not true universally. Due to atmospheric refraction (bending of sunlight) and how sunrise/sunset is measured, daylight tends to be slightly longer. The true equilux (a day when day and night are exactly equal) may occur a few days before or after the equinox, depending on location.
- Autumn always starting on Sept 22 – Many years yes, but sometimes it falls on Sept 23 (or rarely Sept 21/24) depending on how leap years and Earth’s orbit align.
- Equinox = meteorological autumn – Meteorological seasons are based on fixed calendar dates (e.g. September 1). Astronomical seasons depend on Earth’s position. SEO articles need to clarify which one is being discussed.
First Day of Autumn 2025 in Different Time Zones
Because the equinox moment (2:19 p.m. EDT / 18:19 UTC) is a global instant, local times vary. Here are some conversions to help readers around the world:
| Location | Local Time of Equinox, 2025 |
|---|---|
| New York (USA, EDT) | September 22, 2:19 p.m. |
| London (UK, BST) | September 22, about 7:19 p.m. |
| Karachi (Pakistan, PKT) | ~ 11:19 p.m. on September 22 |
| Tokyo (Japan, JST) | ~ 3:19 a.m. on September 23 |
| Sydney (Australia, AEST) | ~ 4:19 a.m. on September 23 |
(These times account for daylight saving in applicable regions.)
First Day of Autumn 2025: What to Expect & How to Celebrate
Knowing the facts is great; making them meaningful is better. Here are ideas and expectations for this seasonal transition:
- Expect cooler mornings and evenings in many regions. If you’re in the Northern Hemisphere, summer warmth lingers, but autumn’s approach will be perceptible.
- Observe nature’s cues: changing leaf colors, birds migrating, sunsets earlier, richer tone of sunlight.
- Celebrate balance: Many traditions use the equinox for rituals of gratitude, release, and planning.
- Photography and outdoor/pick-your-own produce opportunities: apples, pumpkins, fall foliage.
Why First Day of Autumn 2025 Is Unusual (or Not)
While 2025’s start of autumn may feel familiar, a few nuances are interesting:
- 2025’s equinox is happening at a time (2:19 p.m. EDT) that’s mid-afternoon in many U.S. time zones. That means for some, the first part of their “autumn day” is already in the old season (summer) until that time.
- Because of Earth’s tilt and atmospheric effects, the equal-day-night condition (equilux) is not exactly on September 22 everywhere. Depending on latitude, equilux might happen a day earlier or later.
FAQs
Q: Does autumn always start on September 22?
A: No. Due to orbital mechanics and leap years, the autumnal equinox (and thus first day of autumn astronomically) can fall on Sept 21, 22, or 23 (rarely 24).
Q: Is autumn different in the Southern Hemisphere?
A: Yes. What is “autumn” in the Northern Hemisphere equals “spring” in the Southern Hemisphere. Their first day of autumn is based on the March equinox.
Q: What’s the difference between astronomical autumn and meteorological autumn?
A: Astronomical autumn is determined by Earth’s position relative to the Sun (equinox to solstice). Meteorological autumn is based on calendar months and typical temperature patterns. Many weather services use Sept-Nov in the Northern Hemisphere.
The first day of autumn 2025, by astronomical reckoning, is September 22, 2025 at 2:19 p.m. EDT (18:19 UTC). This moment marks the autumnal equinox, when the Sun crosses the celestial equator and day and night are nearly equal. Understanding this date involves knowing which definition of autumn is being used (astronomical vs meteorological), recognizing seasonal and cultural impacts, and appreciating some of the common myths around equinoxes.
