Get ready. If you live anywhere in Europe or the Americas, the “blue moon” is coming to a sky near you Saturday. The phenomenon is mainly due to astronomical arithmetic (and a few mix-ups, but we’ll get to those later).
“It’s how the math works out,” said Philip Hiscock, a folklorist at Memorial University of Newfoundland in Canada. Hiscock is recognized as an authority on the history and folklore surrounding the phrase “blue moon.” The phrase has come to refer to those rare occasions when a second full moon appears within a single calendar month.