Autumnal Equinox

The Autumnal Equinox in September ushers in a change of season. It is observed annually when the sun can be seen directly overhead along the equator. The day marks the end of summer and beginning of fall in the Northern Hemisphere.


The autumn equinox is one of two days when all points on Earth except the polar regions see the sunrise and set at due east and due west. With few exceptions, all latitudes see almost precisely 12 hours of daylight and 12 of darkness.

While the United States marks the official end of summer at Labor Day, the seasons mark time differently. Depending on where we live, the trees and animals behave differently based on the amount of sunlight they receive. By the time the equinox arrives in September, the leaves in many parts of the country have already begun to change. The air at night is crisper.

People’s minds begin to think about warmer clothes and preparing their homes for winter. Since children are already in school, most summer activities have ended. In the fields, farmers eagerly watch for the opportune time to harvest. Apples, pumpkins, and root vegetables ripen in the orchards and gardens. On cool evenings, long walks along the trails under the canopies of gold, umber, violet and crimson keep us warm.


Enjoy a long walk. Sip some tea or watch the sunset. Autumn has arrived. Use #AutumnalEquinox to post on social media.

Educators, visit the National Day Calendar Classroom for projects designed for the Equinox.


Since the dawn of time, the autumnal equinox has marked the passing of one season and the beginning of another. It has influenced the development of calendars, beliefs, customs, cultures, traditions, and much more.

Autumnal Equinox FAQ

Q. What’s the difference between an equinox and a solstice?
A. An equinox is a day in the year when both light and darkness are equal. There are two equinoxes every year – the vernal equinox in the spring and the autumnal equinox in the fall. On these days, there are 12 hours of sunlight and 12 hours of darkness. The solstices include the shortest and longest days of the year. In the Northern Hemisphere, the longest day of the year takes place in June and is called the summer solstice or the June solstice. The shortest day of the year takes place in December and is called the winter solstice or the December solstice.

Q. Do the solstices and equinoxes take place at the same time every year?
A. Solstices and equinoxes occur near the same day every year. The vernal equinox represents the beginning of astronomical spring in the Northern Hemisphere. However, the season each equinox and solstice represents changes by hemisphere.

Q. What’s the difference between meteorological seasons and astronomical seasons?
A. The meteorological seasons are determined by weather. Astronomical seasons are determined by Earth’s and the Sun’s positions in space.