Once in a Blue Moon

This Halloween just doesn’t fall on a Saturday. This year, the skies will match your decor with a dazzling full moon. And not just any full moon — a blue moon. Keep reading to find out more.


A blue moon is the second full moon in a month. The two full moons will be on Oct. 1 and Oct. 31. The average lunar cycle is about 29 days, meaning two full moons don’t usually happen in the same month. Hence the phrase “once in a blue moon.” It doesn’t have anything to do with the color, unfortunately. “Most blue moons look pale gray and white, indistinguishable from any other moon you’ve ever seen,” said NASA. “Squeezing a second full moon into a calendar month doesn’t change the physical properties of the moon itself, so the color remains the same.” That second moon has been called a blue moon since at least 1528, when it was recorded being used in English. The first moon in October, incidentally, is called the Harvest Moon. But on Halloween? Yep. A full moon on Halloween happens once about every 19 years, last occurring in 2001. The next one is set for 2039.

When the phrase “once in a blue moon” was coined, it meant something so rare you’d be lucky to see in your lifetime, according to NASA.

Enjoy your Halloween evening under the blue moon.