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Happy May Day! Today is an astronomy holiday

Posted by
Deborah Byrd
and
May 1, 2025
Children holding on to ribbons off a maypole and church in the background.
Maypole dancing at the village’s fair at Bishopstone, East Sussex, with the tower of St Andrew’s parish church in the background. Image via Kevin Gordon/ Wikimedia Commons (CC BY-SA 2.0 Generic).

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May Day is May 1

You might not realize it, but May Day – an ancient spring festival in the Northern Hemisphere – is an astronomy holiday. It’s one of the year’s four cross-quarter days. That is, it’s a day that falls more or less midway between an equinox and solstice. In this case, it’s between the March equinox and June solstice.

The other cross-quarter days are Groundhog Day on February 2, Lammas on August 1 and Halloween on October 31.

In addition, May Day also stems from the Celtic festival of Beltane. It was related to the waxing power of the sun as we in the Northern Hemisphere move closer to summer. At Beltane, people drove livestock through lit fires and people danced around them. They were all moving in the same direction that the sun crosses the sky.

In Hawaii, May Day is Lei Day, a statewide celebration of the aloha spirit and the giving of the flower lei.

Sphere around Earth with equinoxes, solstices, and cross-quarter days marked.
May Day is a cross quarter day. That is, it’s a day that lies midway between an equinox and a solstice. On this diagram, the 4 cross quarter days are indicated by red crosses. What are you looking at here? The line for the celestial equator – and the line for the ecliptic, or sun’s path across our sky – are really planes. The plane of the celestial equator extends outward from Earth’s equator. The plane of the ecliptic extends between the Earth and sun. Notice that equinoxes happen where those 2 planes intersect. May Day is the year’s 2nd cross quarter day. It falls between the vernal equinox and the summer solstice. What about that outermost circle? Ignore it! It doesn’t mean anything. Illustration via NASA.

May Day and maypoles

Of course, wrapping a maypole with colorful ribbons is perhaps the best known of all May Day traditions. In the Middle Ages, English villages all had maypoles. Indeed, they were part of the rejoicing and raucous merrymaking of May Day.

Maypoles came in many sizes. And there was competition among the villages to show whose maypole was the tallest. In small towns, maypoles were usually set up for the day. But they were erected permanently in London and the larger towns.

Here’s a WikiHow on how to do a maypole dance

May baskets can brighten someone’s day

We’re not too far away from a time in the late 20th century when people left homemade May baskets filled with spring flowers and sweets on others’ doorsteps, usually anonymously. And I can remember doing this as a child. So maybe it’s a tradition that can be revived.

May Day: Group of children holding ribbons off a maypole.
A May Day celebration showing children dancing around a maypole. This took place on the Village Green in Tewin, near Welwyn Garden City, United Kingdom. Image via Paul Barnett/ Wikimedia Commons. (CC BY-SA 2.0 Generic).

Bottom line: May 1 is one of four cross-quarter days, midway between an equinox and a solstice. So, happy May Day 2025!

Read more: Halloween is a cross-quarter day

Read more: Groundhog Day is an astronomy holiday

Posted 
May 1, 2025
 in 
Astronomy Essentials

Deborah Byrd

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About the Author:
Our Editor-in-Chief Deborah Byrd works to keep all the astronomy balls in the air between EarthSky's website, YouTube page and social media platforms. She's the primary editor of our popular daily newsletter and a frequent host of EarthSky livestreams. Deborah created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Prior to that, she had worked for the University of Texas McDonald Observatory since 1976, and created and produced their Star Date radio series. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. In 2020, she won the Education Prize from the American Astronomical Society, the largest organization of professional astronomers in North America. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says.

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