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How often does a Blue Moon occur, and when will there be another?

JULIE MILLER-KLINE, OMAHA, NEBRASKA
What most people mean when they speak of a Blue Moon is the second Full Moon occurring in a single calendar month. This meaning, which dates back to 1946, grew out of a more complex tradition found in farmers' almanacs in the 19th century.Full Moons recur every 29.53 days, just enough for a full cycle to fit snugly within a calendar month every now and then. Blue Moons recur every 2.4 years on average, with about 41 typically occurring each century. The last Blue Moon occurred July 31, 2004, and...

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