What is the origin of the once in a blue moon?
The phrase “once in a blue moon” is a common one in English. It is used to mean a very rare phenomenon, like, “I get a raise once in a blue moon.” But what is a blue moon, and how rare is it? As it happens, a blue moon is not all that rare. A blue moon is not really blue, but actually is the name given to the second full Moon in the same month. It takes the Moon about 29.5 days to go from full through all its phases and back to full again. Since that is less than the days in an average month, it’s possible to have two full Moons in one month (if the first one is early enough in the month).
