As the leaves begin to turn and a familiar chill creeps into the air, many across the Northern Hemisphere find themselves wondering: when, exactly, does autumn begin? The answer, it turns out, depends on whom you ask and which calendar you follow. This year, the arrival of fall is marked by two different systems—meteorological and astronomical—each with its own logic and traditions, but both converging on a season that’s as much about science as it is about culture and memory.
According to The Economic Times, the autumnal equinox—sometimes called the fall equinox—can occur anywhere between September 21 and 24 in the Northern Hemisphere, depending on the year. In 2025, the astronomical autumn begins on Monday, September 22, precisely when the sun’s path aligns with the Earth’s equator, resulting in nearly equal lengths of day and night. This moment, known as the equinox, comes from two Latin words meaning "equal" and "night," a fitting description for this twice-yearly event.
But if you consult meteorologists or weather-watchers, the story is a bit different. As NationalWorld explains, meteorological autumn is based on the Gregorian calendar and annual temperature cycles, making it easier to compare seasonal and monthly statistics. Meteorological autumn always begins on September 1 and ends on November 30, with winter kicking off on December 1. This definition, while perhaps less poetic, offers a practical framework for those tracking weather patterns and climate data.
The astronomical calculation, on the other hand, relies on the Earth’s position relative to the sun. The autumnal equinox marks the start of astronomical autumn, and in 2025, this occurs on Monday, September 22, at around 1:42 pm UK time. On this day, the planet receives roughly 12 hours of daylight and 12 hours of darkness—though, as NationalWorld notes, the Earth’s atmosphere and local geography can cause minor variations in the exact duration of sunlight experienced in different locations.
Why do these two systems exist in the first place? The answer lies in the different needs of scientists and societies. Meteorological seasons, as The Economic Times points out, are tailored for those who need to make sense of long-term weather trends and climate statistics. By dividing the year into four three-month blocks—spring, summer, autumn, and winter—meteorologists create a consistent framework for data comparison. So, meteorological autumn always runs from September 1 to November 30, regardless of what the sun or stars are doing.
Astronomical seasons, in contrast, are rooted in the Earth’s journey around the sun. For most of the year, the planet’s axis is tilted either toward or away from the sun, causing the familiar ebb and flow of daylight and warmth. The equinoxes—autumnal and vernal (spring)—represent those rare moments when the tilt is neither toward nor away, and the sun’s rays strike the equator directly. As The Economic Times explains, this means day and night are nearly equal in length, though one may get a few extra minutes depending on your latitude.
The solstices, meanwhile, mark the extremes: the summer solstice brings the longest day and shortest night, while the winter solstice delivers the shortest day and longest night. In 2025, the winter solstice will fall on Sunday, December 21, according to NationalWorld. On that day, daylight will last just 7 hours, 49 minutes, and 42 seconds—a full 9 hours and 41 minutes shorter than the summer solstice’s sun-drenched peak.
These celestial milestones have not gone unnoticed by human societies. For centuries, cultures around the world have marked the equinoxes with festivals and rituals. The fall equinox, in particular, is often linked to harvest celebrations. In Poland and other parts of Eastern Europe, the Dozynki festival is thought to have originated with the equinox, serving as a time to give thanks for the season’s bounty. Meanwhile, at the ancient Mayan site of Chichen Itza in Mexico, crowds gather to watch the sun create a shadow that resembles a serpent slithering down the steps of the pyramid known as El Castillo—a dramatic reminder of how closely ancient peoples observed the rhythms of the heavens.
But the equinox is not just a relic of the past. Even today, it shapes our experience of time and light. In the United Kingdom, for example, the end of British Summer Time is marked by turning the clocks back every October, a ritual that brings noticeably shorter days and longer nights. Yet, as NationalWorld notes, the official start of autumn comes before the clocks change, underscoring just how many layers of tradition and calculation are woven into our seasonal calendars.
For those wondering exactly when autumn ends, the answer again depends on your preferred system. Meteorologically, the last day of autumn is November 30, with winter beginning on December 1. Astronomically, autumn lasts until the winter solstice, which in 2025 falls on December 21. After that, the gradual return of longer days begins, though the coldest weeks may still be ahead.
It’s easy to see why the shifting of seasons has long captivated poets, scientists, and ordinary folks alike. The equinox, with its promise of balance and symmetry, offers a brief respite before the darkness of winter sets in. As The Economic Times observes, “on the equinox, day and night last almost the same amount of time—though one may get a few extra minutes, depending on where you are on the planet.”
Yet, for all the precision of modern science, there’s still room for a bit of subjectivity—and even a touch of nostalgia. The arrival of autumn means different things to different people: a return to school, the start of harvest, a reason to dig out cozy sweaters and warm drinks. Whether you’re counting the days by the position of the sun or the flip of a calendar page, the transition is unmistakable. The days grow shorter, the nights stretch longer, and the world seems to settle in for a well-earned rest.
So as the autumnal equinox arrives once more, it’s worth pausing to notice the subtle changes—the golden light, the crisp air, the sense that the year is turning. Whether you mark the season by science, tradition, or simple observation, autumn’s arrival is a reminder that, in the grand dance between Earth and sun, we all share in the rhythm of the changing light.
