We’ve just marked the first day of Fall on September 22nd with something called the Autumnal Equinox. As we settle into the falling leaves and pumpkin spice season, you might be wondering what the word equinox actually means, and how it’s different from a solstice.
Every season begins with either a solstice or an equinox. In 2026, the Spring Equinox occurred on March 20, the Summer Solstice was June 21, and the Winter Solstice will be December 21. These dates can shift slightly each year because Earth’s orbit isn’t a perfect circle.
To understand why these events matter, let’s break them down in a way that’s easy to visualize.
Equinox
An equinox happens twice a year when Earth’s tilt lines up so that both hemispheres receive the same amount of sunlight. This is because when the tilt becomes sideways relative to the Sun, neither hemisphere leans toward or away from it.
Equinoxes are said to be the “balance points” of the year. They’re the transition moments when seasons shift and daylight hours begin to noticeably change.
Quick Facts
- Day and night are almost the same length everywhere on Earth.
- The Sun rises exactly in the east and sets exactly in the west.
- Earth’s subsolar point (the spot getting direct sunlight) is right over the equator.
- Marks the first day of Spring (March) and first day of Fall (September).
Solstice
A solstice also happens twice a year, in June and December. However, unlike an equinox, this event occurs when Earth’s tilt is at its maximum angle toward or away from the Sun.
The solstices mark the seasons where days begin to get longer or shorter by daylight. The Summer Solstice is the longest day of the year, whereas the Winter Solstice is the shortest of the year. Here are a few more quick facts:
Summer Solstice:
- Sun is at its highest point in the sky
- Northern Hemisphere is tilted toward the Sun
Winter Solstice:
- Sun is at its lowest point in the sky
- Northern Hemisphere is tilted away from the Sun
The Seasons
These four events shape the changing of our seasons and explain why the hours of sunlight in a day change throughout the year. Now that you know solstices and equinoxes are determined by Earth’s tilt and orbit, seasons and daylight might make a lot more sense.