First Day of Fall: When Is the Autumnal Equinox?

The autumnal equinox—the precise moment the Sun crosses the celestial equator—marks fall’s official debut in the Northern Hemisphere. In 2025, that moment arrives on September 22 at 18:19 UTC, though the date drifts between September 21 and 24 depending on Earth’s orbit around the Sun.

Typical Date: September 22 or 23 ·
2025 Date: September 22 at 18:19 UTC ·
2026 Date: September 23 at 00:06 UTC ·
Range Possible: September 21 to 24

Historical records reveal a clear pattern in September equinox timing across recent years.

What is officially the first day of fall?

The official first day of fall in the Northern Hemisphere is the autumnal equinox. That’s the moment the Sun crosses the celestial equator moving southward, and it’s the astronomical signal that summer is over and autumn has begun. For most years, this happens on September 22 or 23.

Astronomical definition

Astronomically speaking, the equinox marks when Earth’s rotational axis points neither toward nor away from the Sun, creating a day with roughly equal sunlight and darkness worldwide. The term “equinox” comes from the Latin words for “equal night,” according to Space.com. During the 2025 equinox, the Sun appears directly overhead from a point in the equatorial Pacific, approximately 1,320 miles south-southeast of Acapulco, Mexico.

Meteorological definition

Meteorologists define fall differently: meteorological autumn always begins on September 1, ending on November 30. This system groups seasons into neat three-month blocks to keep weather records consistent, as noted by Royal Museums Greenwich. The meteorological approach ignores the actual position of the Sun, instead using temperature patterns to mark seasonal transitions.

Is September 22 always the first day of fall?

No—September 22 is the most common date for the autumnal equinox, but it isn’t fixed. The equinox can fall anywhere between September 21 and September 24, a range that stems from the mismatch between our calendar system and Earth’s actual orbit around the Sun, according to Wikipedia.

Reasons for date variation

A tropical year—the time it takes Earth to complete one orbit relative to the seasons—is approximately 365.24 days, not an exact multiple of 24 hours. This means the equinox drifts roughly six hours later each calendar year, occasionally spilling over into the next day. Leap years reset the clock, which is why equinox dates bounce between September 21 and 24.

Historical examples

Recent equinox times illustrate this drift clearly. According to Wikipedia’s compiled records, the autumnal equinox occurred on September 22 in 2021 (19:21 UTC) and 2024 (12:44 UTC), but shifted to September 23 in 2022 (01:04 UTC), 2023 (06:50 UTC), and 2026 (00:06 UTC). The 2025 equinox lands back on September 22 at 18:19 UTC.

What and when is the autumnal equinox?

The autumnal equinox is a precise astronomical event, not an approximate one. It’s the moment when the Sun crosses the celestial equator traveling south, marking the official start of fall for roughly 90% of Earth’s population in the Northern Hemisphere.

Equinox meaning

During the equinox, the Sun rises due east and sets due west—a phenomenon visible worldwide, including at the equator. The term “equinox” literally means “equal night” in Latin, referring to the theoretical balance of daylight and darkness across the planet, according to Sky at Night Magazine. After the equinox, the Sun’s rising and setting points shift progressively southward in both hemispheres, shortening days for Northern Hemisphere residents.

Exact timing

For 2025, the equinox occurs on September 22 at 18:19 UTC, which translates to 2:19 p.m. Eastern Daylight Time in the United States, reports Space.com. In the United Kingdom, observers see the event at 19:20 BST—a minor one-minute discrepancy from Sky at Night Magazine’s stated 18:20 UTC.

“In 2025 the autumn equinox occurs on 22 September at 19.20 BST, marking the day when we experience roughly the same amount of daytime and nighttime.”

— Sky at Night Magazine, astronomy experts

When is the first day of fall in 2025?

The first day of fall in 2025 falls on Monday, September 22. At 18:19 UTC (2:19 p.m. EDT), the Sun crosses the celestial equator and astronomical autumn officially begins in the Northern Hemisphere. The event is visible simultaneously worldwide, though local times differ based on timezone.

2025 to 2027 dates

Recent equinox records show the pattern clearly. According to Wikipedia’s compiled data: the 2024 equinox arrived on September 22 at 12:44 UTC; 2025 follows on September 22 at 18:19 UTC; and 2026 shifts to September 23 at 00:06 UTC. The 2027 equinox is expected to land back on September 22 or 23.

2033 outlook

Long-range projections suggest the equinox will continue its September 21–24 pattern through at least 2033. The specific date depends on leap year cycles and the ongoing drift caused by the tropical year’s 365.24-day structure, though no official ephemeris tables for that year were available from Tier 1 sources.

“A carefully worded answer is that on Monday, Sept. 22, at 2:19 p.m. Eastern daylight time… autumn begins astronomically in the Northern Hemisphere.”

— Space.com, astronomy journalists

Why do Americans call it fall?

The word “fall” as a term for the autumn season is distinctly American, though it’s now understood worldwide. The name traces back to the phrase “fall of the leaf”—the visible shedding of foliage that marks the season’s arrival.

Autumn vs. fall usage

The word “autumn” is more common in British English and predates “fall” etymologically, coming from the Latin “autumnus.” American English adopted “fall” in the 18th century, likely as a shortening of the earlier “time of falling leaves.” Both terms are correct, though American publications and speech overwhelmingly favor “fall.”

Regional preferences

British English speakers typically use “autumn” almost exclusively, while American English speakers use both but prefer “fall” in everyday conversation. International weather reports and scientific publications usually default to “autumn” for clarity across dialects.

What are the 3 fall months?

The three months of fall in the Northern Hemisphere are September, October, and November. This aligns with both the meteorological and astronomical definitions of the season, though meteorological fall always runs from September 1 through November 30, while astronomical fall begins at the equinox and ends at the winter solstice.

Is October 21st the first day of fall?

No—October 21st is not recognized as the first day of fall by any standard astronomical or meteorological definition. The autumnal equinox in the Northern Hemisphere occurs in September, not October. Some cultures or regions may have alternative seasonal markers tied to local weather patterns or agricultural cycles, but no verified source identifies October 21 as a seasonal milestone.

What is the first day of fall called?

The first day of fall is called the autumnal equinox. The term “equinox” comes from Latin, meaning “equal night,” reflecting the approximately equal balance of daylight and darkness worldwide on that date. In the Northern Hemisphere, the autumnal equinox marks the astronomical beginning of fall.

Is the first day of fall the same every year?

No—the first day of fall varies slightly each year. The equinox can fall anywhere between September 21 and September 24. This variation occurs because the tropical year (approximately 365.24 days) doesn’t align perfectly with our calendar system. The equinox drifts about six hours later each year until a leap year resets the pattern.

What country has the longest autumn?

No verified source definitively identifies a single country as having the “longest autumn.” While some regions experience prolonged fall-like conditions based on geographic features, climate patterns, and microclimates, no official designation exists for which country claims this distinction.

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