Spring Equinox 2023: What Exactly Is It?

Star Walk
7 min readMar 20, 2023
Image Credit: Vito Technology, Inc.

Here is everything you need to know about the vernal equinox: its definition, dates, how it relates to the seasons, and the most popular myth about it.

  • What is it?

The spring equinox (as well as autumnal equinox) is the moment when neither of the Earth’s hemispheres is inclined towards or away from the Sun.

  • When is it?

In the Northern Hemisphere, the spring equinox this year will take place on March 20, 2023, at 21:25 GMT (4:25 p.m. EST). In the Southern Hemisphere, it will occur on September 23, 2023, at 06:50 GMT (2:50 a.m. EDT). With the Sky Tonight app, which gives you a full calendar of astronomical events and lets you set alerts, you won’t miss the event.

  • Why is it important?

In astronomy, the vernal equinox marks the first day of spring (as the name suggests). So the beginning of a new season is celebrated worldwide with various spring traditions, holidays, and festivals. Spring equinox also signals the return of sunshine, warmer temperatures, blooming flowers, and other seasonal effects that are noticeable to everyone.

What is the spring equinox?

As mentioned above, equinoxes occur when the Earth’s hemispheres aren’t tilted towards or away from the Sun. As a result, the Sun is located directly above the equator, and both hemispheres receive an almost equal amount of sunlight. After the spring equinox, the relevant hemisphere (northern one in March and southern one in September) tilts closer to the Sun, resulting in more hours of daylight, with earlier sunrises and later sunsets.

At the moment of the equinox, the ecliptic and the celestial equator intersect. The ecliptic is the Sun’s path across the sky; the celestial equator is an imaginary line extending from the Earth’s equator into the celestial sphere. They are inclined to each other at 23.5°. If there were no inclination between them, there would be no seasons and solstices, and we would have the equinox all year round.

As we mentioned, the spring equinox takes place in March or September. It depends on your latitude. How come? Let’s figure it out.

What is March equinox & September equinox?

If you live in the Northern Hemisphere, you probably use the terms “March equinox” and “vernal equinox” interchangeably because, in this region, the March equinox marks the beginning of spring and all the seasonal changes that come with it.

In the Southern Hemisphere, however, the seasons are reversed. That’s why there the March equinox symbolizes the beginning of autumn and therefore is called the “autumnal” equinox.

To avoid confusion between the different hemispheres, astronomers use the terms “March equinox” and “September equinox”. In everyday life, however, you’re more likely to hear about the “vernal” and “autumnal” equinoxes.

When is the spring equinox 2023?

In the Northern Hemisphere, the spring equinox takes place on March 20, 2023, at 21:25 GMT (4:25 p.m. EST).

In the Southern Hemisphere, the spring equinox takes place on September 23, 2023, at 06:50 GMT (2:50 a.m. EDT).

To find out the exact equinox time for your time zone, open the Sky Tonight app. Go to the search window and enter “Equinox” in the search field. You’ll see the exact time of the event in your location in the corresponding search result.

Another way is to use a time converter, like worldtimebuddy.com.

Spring equinox dates

In the Northern Hemisphere, the spring equinox dates vary between March 19 and 21. In this century, 78 equinoxes fall on March 20, and only two occur on March 21. The other 20 equinoxes this century occur on March 19.

In the Southern Hemisphere, the dates of the vernal equinox vary between September 21 and 24. In the 21st century, the most common equinox date is September 22 — it occurs on this day 76 times. Meanwhile, the next equinox on September 24 will take place only in 2303.

Note that the dates above are given in the Greenwich Mean Time (GMT), and the equinox date may vary in different time zones.

Here are the spring equinox dates for five years:

Northern Hemisphere

  • 2023: March 20, 21:25 GMT (4:25 p.m. ET)
  • 2024: March 20, 03:07 GMT (10:07 p.m. ET)
  • 2025: March 20, 09:02 GMT (04:02 a.m. ET)
  • 2026: March 20, 14:46 GMT (09:46 a.m. ET)
  • 2027: March 20, 20:25 GMT (03:25 a.m. ET)

Southern Hemisphere

  • 2023: September 23, 06:50 GMT (2:50 a.m. ET)
  • 2024: September 22, 12:44 GMT (08:44 a.m. ET)
  • 2025: September 22, 18:20 GMT (02:20 p.m. ET)
  • 2026: September 23, 00:06 GMT (September 22, 08:06 p.m. ET)
  • 2027: September 23, 06:02 GMT (02:02 a.m. ET)

When is the first day of spring 2023?

Spring in the Northern Hemisphere begins on March 20, 2023, at 21:25 GMT (4:25 p.m. EST). In the Southern Hemisphere, spring starts on September 23, 2023, at 06:50 GMT (2:50 a.m. ETD). This is consistent with the astronomical approach, which suggests that the equinoxes mark the transition from winter to spring and from summer to autumn. The dates of these events are based on the Earth’s position in relation to the Sun and can change from year to year.

The meteorological approach suggests that spring starts on March 1 (or September 1 for southern latitudes). Such an approach is based on annual temperature cycles. It also follows the Gregorian calendar and has fixed dates that help to divide a year into equal quarters and make it easier to compare monthly and seasonal statistics.

Equal day and night 2023: debunking the most popular myth

Despite the common misconception, the length of day and night at the equinox is almost equal, but not exactly the same. There are two reasons for this — atmospheric refraction, and the definition of sunset/sunrise.

Atmospheric refraction

The Earth’s atmosphere scatters sunlight and affects the length of daylight. When a wave (sunlight) encounters a medium (the Earth’s atmosphere) whose density is different from that through which the wave has been propagating, the direction of the wave changes. To imagine how it works, think of a pencil in a glass of water — the pencil appears to bend when viewed from certain angles.

We know that our atmosphere uplifts the Sun by about 0.5 degrees from its true position whenever the Sun is near the horizon. This means that when you see the Sun near the horizon, in reality, it’s already below the line. However, the atmosphere bends the light upwards, making the Sun appear in a different place.

Regarding the daylight length, atmospheric refraction advances sunrise and delays sunset, adding about 8 minutes of sunlight.

Sunset/sunrise definition

If sunset and sunrise were defined as the moments when the geometric center of the Sun passes over the horizon, we would have exactly 12 hours of day and 12 hours of night. But this isn’t the case. Sunrise and sunset are defined as the exact moments when the upper edge of the Sun touches the horizon. So the time it takes for the Sun to disappear completely below the horizon (which can be several minutes) makes the day slightly longer than the night on the equinox.

Daylight length on the spring equinox

Here is the list of different places and the length of daylight there on the vernal equinox on March 20, 2023. The length of the day will be about the same all over the world — even in the Southern Hemisphere, where the autumnal equinox occurs on this day.

  • New York City, USA: 12 hours, 8 minutes
  • Amsterdam, Netherlands: 12 hours, 9 minutes
  • Longyearbyen (one of the northernmost cities), Norway: 12 hours, 25 minutes
  • Rio de Janeiro, Brazil: 12 hours, 7 minutes
  • Melbourne, Australia: 12 hours, 10 minutes
  • Amundsen–Scott South Pole Station: 24 hours
  • Summit Camp, US North Pole Station: 24 hours*

*Daylight on the day of the equinox lasts 24 hours on both poles, regardless of whether it is the autumnal or spring equinox. At the North Pole, polar night (24 hours of darkness) turns into polar day (24 hours of daylight) a few days before the equinox, while at the South Pole polar day turns into polar night a few days after the equinox.

Equilux: equal day and night

Although day and night aren’t exactly equal at the equinox, there is the equilux. This word is used to describe days when day and night are equal. Equiluxes happen a few days before the vernal equinox (and a few days after the autumnal equinox). On such a day, we experience as close to 12 hours of daylight as possible (give or take a few tens of seconds). The exact day of equilux depends on latitude.

F.A.Q.

When is spring solstice?

There is no such thing as a “spring solstice”, only the “spring equinox”. Remember: solstices occur in June and December; equinoxes — in March and September. To ensure you know the difference between these two events, take our quiz on equinoxes and solstices.

When is spring 2023?

Depending on the approach, spring in the Northern Hemisphere starts either on the vernal equinox (March 20, 2023) or on March 1. Astronomers count the solstices and equinoxes as the transition points between the seasons, while meteorologists consider the seasons to begin on the first day of the months that include the equinoxes and solstices. For more information, read our dedicated article.

What is the first Full Moon after spring equinox 2023?

The first Full Moon after the spring equinox in the Northern Hemisphere will take place on April 6, 2023. It’s called the Pink Moon and denotes the season when a wild pink flower — Phlox subulata — blooms. Learn the dates of other Full Moons this year from our Full Moon 2023 Calendar.

Bottom line

Spring equinox takes place on March 20, 2023, in the Northern Hemisphere, and on September 23, 2023, in the Southern Hemisphere. It marks almost equal lengths of day and night, although the amount of daylight is slightly greater. In astronomical terms, it symbolizes the first day of spring.

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