Blue Moon New Year’s Eve

By Amanda Pendolino on December 30th, 2009

blue-moon-1 Have you ever heard the saying “Once in a blue moon?” Me neither. Just kidding. This New Year’s’ Eve, you can finally find out what it means. According to CNN, the moon won’t actually start turning blue (at least not until you see the bottom of your champagne bottle. The phrase simply refers to the second full moon in a calendar month, something that NASA says hasn’t happened on a New Year’s Eve for nearly 20 years.

“December 1990 ended with a blue moon, and many New Year’s Eve parties were themed by the event,” said Professor Philip Hiscock of the department of folklore at Memorial University of Newfoundland, in Canada. “It was a lot of fun.” (Or at least as much fun as you can have when you work in a department of folklore.)

Most months have just one full moon, because the 29.5-day cycle of the moon matches up pretty well with the length of calendar months. Occasionally, there will be two full moons in a month, something that happens about every 2½ years, NASA says.

As for the moon actually looking blue: it’s possible, but that’s sometimes caused by fine dirt circulating in the Earth’s atmosphere or the dark blue tone of the sky.

“The phrase ‘blue moon’ has been around a long time, well over 400 years, but during that time its meaning has shifted,” Hiscock said. So you might say a blue moon on December 31 comes once…in a blue moon.