Autumn Equinox 2025: What it is, when it falls, and some interesting facts

Summer 2025 is officially coming to a close. Despite the rise in temperatures in recent days, the season of beach holidays, sunsets, and endless days will soon be over. Indeed, the autumnal equinox , the symbolic moment marking the transition to the new season, is very close. In 2025, it will fall on Monday, September 22nd, and from that precise moment, a significant temporal-seasonal shift will occur: in the Northern Hemisphere, autumn will officially begin, while in the Southern Hemisphere, spring will begin.

But what exactly is the equinox? Why doesn't it always fall on the same day? And what scientific and spiritual significance does this event, which has fascinated cultures around the world for millennia, bring?

What is the autumnal equinox and what happens?

The word "equinox" comes from the Latin aequus nox , meaning "equal night." It is the moment when the Sun is directly above the celestial equator and the sun's rays strike the Earth perpendicularly. In theory, this would result in perfectly equal hours of daylight and darkness across the planet. In reality, things are a little more complex: due to atmospheric refraction, which causes the Sun to appear on the horizon a few minutes before it actually rises, and the official calculation of sunrise (linked to the first visible ray), the equinox day always offers a few extra minutes of daylight.

The actual day when the budget is perfectly balanced is called “equilux” and falls a few days later.

When does the autumn equinox fall in 2025?

The equinox isn't a whole day, but a precise moment . In 2025, the date to mark on your calendar is Monday, September 22nd . The time? 6:19 PM UTC , which corresponds to 8:19 PM Italian time . It will be at that exact moment that we will say goodbye to summer, welcoming with open arms the season of foliage , the smell of cinnamon, and the shortening days. There are those who love all this and those who, instead, would like to stay in summer forever.

Why does the autumnal equinox change date every time?

As is often the case with other seasonal events, the autumnal equinox doesn't always fall on the same date. It can, in fact, fluctuate between September 21st and 24th, and the reason for this fluctuation lies in the difference between the solar calendar year (therefore the 365-day year) and the sidereal year , which is the time it takes the Earth to complete one revolution around the Sun (365 days, 6 hours, and 9 minutes). This seemingly minimal discrepancy, offset by the introduction of leap years, causes the equinox to shift slightly from one year to the next.

When does autumn begin? The three definitions

The beginning of autumn can be interpreted in different ways and the classification that is made generally includes three main strands:

• Astronomical autumn : it is based on equinoxes and solstices, it identifies the autumnal equinox as the official moment of transition;
• Meteorological autumn : Climatologists divide the year into quarters based on average temperatures. In this scheme, autumn coincides with September, October, and November;
• Phenological autumn : follows nature's signals, such as leaf fall, fruit ripening, or bird migration.

Autumnal Equinox: Curiosities

The autumnal equinox isn't just an astronomical event: according to NASA, during this time, the alignment between Earth and the Sun amplifies the interaction with the solar wind, opening "fissures" in Earth's magnetic field. The result? A greater chance of observing spectacular aurora borealis , which appear twice as often as during the rest of the year.

But beyond its scientific dimension, the autumn equinox has always had a strong symbolic value . The parity between day and night becomes a metaphor for inner balance , thus an invitation to pause and reflect. It is no coincidence, in fact, that we often speak of cosmic balance, when the perfect symmetry between light and darkness recalls the individual need to seek harmony in our lives as well. Furthermore, the autumn equinox is often associated with a return to measure : what does that mean? With the transition from summer to autumn, the end of summer's abundance is symbolically marked and a different time of purification and simplification is ushered in. A kind of detox, to use a contemporary term.

Last but not least, the autumn equinox is synonymous with " personal assessment ." Just as nature brings its harvest to a close, we too, as humans, are compelled to take stock, asking ourselves what we have sown and what fruits we are reaping.

How is the autumn equinox celebrated around the world?

The equinox has been celebrated for millennia in various cultures. Among the celebrations that continue to bear witness to this today are: Two celebrations, in particular, still bear witness to this today:

• Mabon, the pagan festival of balance. Born from Celtic traditions and rediscovered in modern times, Mabon is one of the eight festivals of the neopagan "wheel of the year." It is a thanksgiving for nature's gifts, but also an invitation to introspection;
• The Mid-Autumn Festival in China (or Moon Festival) has been celebrated for over 3,000 years on the fifteenth day of the eighth month of the Chinese calendar, coinciding with the brightest full moon of the year. A symbol of family reunion and cosmic harmony, it unites the lunar element with the seasonal cycle, connecting nature and spirituality.

On Monday, September 22, 2025 , when the Sun crosses the celestial equator, not only will the season change, but also the way we perceive time, nature, and everything related to our personal lives. The autumn equinox begins with astronomy, but it is precisely from astronomy that the awareness of being part of a larger cycle arises, made of sun and darkness, of harvests and new sowings. Welcome autumn 2025.