What is the Difference Between Equinox and Solstice?

The Earth’s seasons change because the planet is slightly tilted as it moves around the Sun. This tilt makes different places on Earth get more or less sunlight at differing times of the year. Two important events mark these changes: solstices and equinoxes. They are not the same; they are opposites.

If Earth were not tilted, the sun would always shine directly over the planet’s middle, equator. Every place would get the same amount of light every day. Seasons would not exist, and there would be no need for solstices or equinoxes.

Equinox (vernal & autumnal)

An equinox happens when the sun is directly above the middle of the Earth. This is the only time of the year when the planet’s top half (Northern Hemisphere) and the bottom half (Southern Hemisphere) get nearly the same amount of daylight and darkness.

Equinoxes happen twice a year. One occurs around March 20, and the other happens around September 22. During these times, sunlight shines directly over the Equator.

Vernal equinox

The vernal equinox also known as spring equinox or March equinox, marks the start of spring in the Northern Hemisphere and fall in the Southern Hemisphere. The opposite happens in September when fall begins in the Northern Hemisphere and spring starts in the Southern Hemisphere.

The date of the March equinox can shift slightly over the years. It usually falls on March 20, but in rare cases, it can happen as early as March 19 or as late as March 21. This shift occurs due to the way the calendar keeps track of time.

Autumnal equinox

The autumnal equinox, or September equinox, occurs when the sun moves directly over the Equator, heading toward the Southern Hemisphere. This event usually takes place between September 21 and 24.

On this day, people standing on the Equator will see the sun rise exactly in the east and set exactly in the west. Before this equinox, the sun appears to rise and set slightly farther north. Afterward, the sun moves southward.

In the Northern Hemisphere, the September equinox signals the start of autumn. However, it marks the beginning of spring for the Southern Hemisphere.

Solstices (summer & winter)

A solstice happens when one of Earth’s poles tilts as far as possible toward or away from the sun. This event occurs twice a year and marks the longest and shortest days.

Summer solstice

The summer solstice is when the sun reaches its highest point in the sky, creating the longest day and shortest night of the year. In the Northern Hemisphere, this happens around June 20, 21, or 22.

In the Southern Hemisphere, it occurs around December 20, 21, 22, or 23. The sun does not set at the poles, and daylight lasts 24 hours.

Winter solstice

The winter solstice is the opposite. The sun is at its lowest point in the sky, bringing the shortest day and longest night.

In the Northern Hemisphere, this happens around December 21 or 22. In the Southern Hemisphere, it occurs around June 20 or 21. At the poles, there is complete darkness or only dim light during this time.