re: #468 DEZes

Just for the hell of it, Some maybe aware blue moons are not that rare.
The person 1st to tell me the average number of blue moons in a year gets an upding.
If you want 2 updings describe a blue moon is a separate post.

And as others have already said, it’s commonly the second full moon occurring within a single month. Although the history of the phrase is more muddled; see the link on my previous post.