So why DO we say "once in a blue moon?" 🌕 This week, we’re getting a Blue Moon!�It’s a rare event that happens when we get thirteen full moons in a calendar year instead of twelve. The lunar cycle is about 29.5 days long, so we usually get one full moon a month, twelve full moons a year (the word "month" comes from "moon"). But just like with leap years, it doesn't line up exactly and that leftover time accumulates, so every two-three years, we get THIRTEEN full moons. The “extra” full moon is