If you need another reminder to move the clocks back early this coming Sunday, go outside and look up.
That full moon on Saturday, on Halloween, is a rare thing — the second full moon in a calendar month.
It’s been 19 years since Halloween came on the day of a full moon. It won’t happen again until Oct. 31, 2039.
According to Jeffrey L. Hunt, an astronomy educator, it’s been even longer since a Halloween full moon arrived that was visible to most people around the globe. That last happened in 1944, he writes.
“No, it’s not Comet Halley, but it’s been 76 years in the making, a Halloween Full Moon that is visible nearly across the entire globe,” Hunt writes.
The Farmers’ Almanac staff got excited about this week’s lunar appearance many moons ago. “In January, we promised our readers that 2020 would be a stargazer’s treat, especially when it came to full moons,” the publication says. The year will bring 13 full moons, including the Halloween moon, which comes only every 19 years.
That 19-year cycle was discovered a long time ago. It is known as the Metonic Cycle because of a Greek astronomer, Meton. That Athenian stargazer is credited with figuring out this lunar cycle in 432 B.C. It became the basis of the ancient Greek calendar.