Why the ‘Blue Moon’ on 31st May isn’t actually blue (and the rare times it was)

ORIGIN: https://www.yourweather.co.uk/news/

Every two to three years, skywatchers get excited about the Blue Moon. We know it is never blue, but does that mean no one has ever seen a Blue Moon?

Blue Moon’s occur every two to three years. But why are they called so?

The run-up to next Sunday, May 31st, will be filled with stories about the Blue Moon and why it is so special. Even if you have been an occasional sky gazer, you are sure to know that the Moon isn’t going to be blue at all. So, why does everybody keep calling it that?

The story of The Blue Moon is a prime example of how a historical mistake becomes something most people continue to follow unquestioningly.

Once is a Blue Moon

Literature studies show that the phrase ‘Once in a Blue Moon’ started circulating around 1823 after being published in the Classical Dictionary of the Vulgar Tongue and had no astronomical origins. But after almost a century, people began looking for one.

In 1937, H.P. Trefethen, the editor of Maine Farmer’s