What is a Blue Moon? And why is it called a Blue Moon? There’s been a lot of hype. Get the scoop here.
When is the Blue Moon?
Blue Moon is not an astronomical term. However, in the media, it’s come to mean the second full Moon of the month. Most months have one Full Moon, not two. See the Almanac Moon Phase Calendar.
Why is it Called the Blue Moon?
We got a lot of letters about this. Some folks imagine that it actually appears blue. Others assume it’s a term that originated with Native American folklore. Neither is true.
The inside scoop is that calling any month’s second full Moon a Blue Moon only started in the 1940s as a result of a mistake in an astronomy magazine.But it slowly went viral until nowadays the second full Moon in the same calendar month is widely called a Blue Moon.
The notion has no venerable pedigree among Native Americans, ancient cultures, or anything in the actual sky. So OK, we’ll play along and call it a Blue Moon. Just so you know, it’s a new idea.
Ever heard the expression, “Once in a Blue Moon?” It suggests great rarity. In reality, since the Moon’s period of phases is 29 ½ days, while months usually have 30 or 31 days, it’s obvious that if a full Moon lands on the first day of any month except February it will repeat again at the end.
Turns out, Blue Moons happen every 30 months on average. Two and a half years.
Not so very rare. Once in a Blue Moon? Stick around!
Are you a Moon lover? Use our Moonrise and Moonset calculator to find out when you can see the Moon!