Every so often social media lights up with warnings and excited posts claiming that the Moon is about to glow bright green for the first time in 420 years. Some versions pin the date to April 20, others pick a different night, but the claim is always the same: a rare “green Moon” is coming soon. As you might guess, there is no such event on the astronomical calendar.

Where the “green Moon” rumor came from

Fact-checking sites and astronomy outlets trace the modern green Moon myth back to a meme that began circulating on Facebook in 2016. It declared that the Moon would turn green on May 29 due to its proximity to the planet Uranus, and that it would be the first time this happened in 184 or 420 years, depending on the version of the post.

The joke really took off when the date was changed to April 20 – 4/20 – which many people associate with cannabis culture and the color green. Articles on EarthSky, Space.com, and Snopes all pointed out the “420 years” detail as another wink at that reference rather than a serious scientific claim.

Could the Moon actually look green?

The Moon itself is not green. If its surface truly had that color, we would see it every clear night, not once in several centuries. Astronomy writers note that the Moon can appear orange or reddish during a lunar eclipse, or when it is low on the horizon and its light passes through more of Earth’s atmosphere, but a green tint is not part of normal lunar behavior.

In theory, unusual atmospheric conditions – like heavy pollution or fine particles in the air – might slightly shift the color of moonlight as we see it from the ground. Even then, astronomers say you would expect subtle changes, not a vivid emerald disc looming in the sky. In most “green Moon” photos that circulate with the rumor, the color has simply been added or boosted digitally.

Why the hoax keeps coming back

Once the original meme went viral, it began resurfacing every few years with new dates and slightly altered explanations. Local news outlets and astronomy magazines now treat it as a recurring internet legend that has to be debunked whenever search interest spikes again.

The posts also tend to include a call to action like “share this with your friends,” which helps the hoax spread. Combine that with dramatic edited images, a specific date, and a fun connection to 4/20, and you have a piece of click-bait that keeps finding new audiences.

How to respond when you see a “green Moon” warning

• If a post promises a dramatic one-night-only sky event and you have never heard about it from mainstream astronomy sources, be skeptical.
• Check an astronomy site, a reputable news outlet, or a fact-checking site before sharing. If a real celestial event were coming, observatories and space agencies would be talking about it.
• Remember that edited photos can make the Moon look almost any color. A picture alone is not proof.

The bottom line: if someone tells you to mark your calendar for the next green Moon, you can safely ignore it – or use it as an excuse to talk about how real lunar eclipses and Supermoons actually work.

Sources

• EarthSky – explanation of the recurring “green Moon on April 20” hoax.
• India Today – background on how the green Moon meme began and spread.
• BBC Sky at Night Magazine – discussion of the myth and whether the Moon could ever appear green.
• Newsweek – coverage of the hoax and its connection to cannabis “4/20” culture.
• TechTimes – article on the 2018 resurgence of the rumor.