As the calendar advances, the autumn equinox once again marks the change of season in the northern hemisphere. This year the event arrives on time and with a defined time, an astronomical moment in which the daylight and night balance each other almost equally before the days begin to shorten more rapidly.
From that moment on, we will notice that the Sun sets earlier and rises later, and it will do so with greater intensity in these initial weeks. This year's autumn will have 89 days and 21 hours of duration, until Winter Solstice and the coldest season begins.
What is the autumnal equinox?
The equinox is the moment in which the Sun crosses the celestial equator, so that its rays fall almost perpendicularly on the terrestrial equator. That is why, all over the planet, day and night have practically the same durationThe word comes from the Latin “aequinoctium,” literally “equal night.”
It occurs twice a year: in March and September. In the Northern Hemisphere, September ends summer and ushers in autumn, while in the Southern Hemisphere it marks the beginning of autumn. springAfter the equinox, the Sun continues its apparent journey south until the December solstice.
Date and time: this is how the beginning of autumn arrives
According to the National Astronomical Observatory (IGN), autumn begins on Monday, September 22th at 20:19 p.m. (Spanish peninsular time). In the Canary Islands it will be at 19:19, and in coordinated universal time, at 18: 19 UTC.
If we look at other time zones, the exact time will be at 14:19 PM ET or 12:19 in Mexico CityIn all cases, we are talking about the same instant, converted to each local time zone.
It is important to distinguish between astronomical seasons and meteorological. The first is defined by phenomena such as the equinox, while the second, for statistical convenience, starts from the September 1. Furthermore, the date of the equinox is not fixed: due to the actual length of the year (approx. 365,2422 days) and the adjustment of the calendar to leap years, the beginning of autumn may fall on 22 or 23 from September throughout the 21st century in official Spanish time.
Equinox, solstice and the length of the day
The difference with a solstice is clear: in the equinox The Sun is located on the celestial equator and balances the duration of day and night, while in the solstice It reaches its maximum decline to the north or south, giving rise to the longest day or the longest night of the year depending on the hemisphere.
After the September equinox, the daily sunlight time in our latitudes decreases rapidly: at the beginning of autumn the Sun is above the horizon almost three minutes less each dayIn mainland Spain, this translates into slightly later sunrises and earlier sunsets, bringing us closer to the day with fewer hours of sunshine.
This period also includes the change to winter time in Spain: during the early morning of Sunday, October 26 The clock will have to be set back one hour. This isn't an astronomical effect of the equinox, but rather a regulatory decision to make better use of daylight hours.
The autumn sky and the traditions that accompany it
The start of the season is accompanied by several meteor showers and full moons Among the former, the Draconids usually reach their maximum in early October, the Orionids at the end of that month, the Leonids in mid-November and the Geminids in mid-December. The autumn full moons will fall on October 7, November 5, and December 5.
Beyond skywatching, the equinox has been a cultural milestone since ancient times. In places like Chichén Itzá (Mexico), the sunlight projects a “snake” effect on the steps at this time; and in Angkor Wat (Cambodia) The alignment of the equinox sunrise with the central tower reflects the astronomical knowledge of its builders.
Cities also celebrate it. In Cuenca, for example, a cultural day in Taiyo Square around the equinox, with music, storytelling, and an astronomy outreach talk, showing how science and culture can go hand in hand to welcome the season.
Anyone who wants to take advantage of the date to look at the sky can look for a clear horizon towards the east at sunrise and west at sunset; near the equinox, sunrises and sunsets approach these cardinal points, making it easier to orient and better understand the phenomenon.
With the arrival of the equinox, the northern hemisphere enters fully into autumn and the south begins spring; an instant of apparent balance which serves as a reference for calendars, observation plans, and traditions. The date and time set the appointment, but what follows is a period of transition: fewer hours of daylight, cooler temperatures, and a sky with appointments marked for anyone who looks up.
