Industry stats show that by late December the end-of-the-world disaster flick 2012 had grossed $730 million worldwide. This suggests that lots of you have seen it.

But not me. I've got more important things to worry about than this market-driven piece of trumped-up hysteria. After all, an even more alarming calamity awaits us on New Year's Eve: a full Moon — the second one in December.

I couldn't believe that doomsayers had overlooked this dread portent, so I double-checked my facts. Yep, it's all right there on page 52 of December's Sky & Telescope: full Moons occur on December 2nd at 7:30 Universal Time, and again on the 31st at 19:13 UT. Running the numbers, I calculate that those two events take place 29.488 days apart — amazingly close to the Moon's average synodic month of 29.531 days.

And did I mention that late on December 31st there'll also be a partial lunar eclipse, visible from Europe and Asia? And for all this to occur on the final day of 2009, the end of the dread decade of the 00s, the Uh-ohs? Can this all be mere coincidence?

Seriously, I doubt the world will grind to a halt on New Year's Eve. After all, the circumstances were the same 19 years ago, on December 31, 1990 — and there were no global consequences (apart from the debut of the Sci-Fi Channel on cable television).

In modern usage, the second full Moon in a month has come to be called a "Blue Moon." But it's not! This colorful term is actually a calendrical goof that worked its way into the pages of Sky & Telescope back in March 1946. There author James Hugh Pruett wrote how two full Moons fall in a single month seven times every 19 years. He then stated, "This second in a month, so I interpret it, was called Blue Moon."

Pruett's interpretation might have faded into history and been forgotten, had my old friend Deborah Byrd not picked up on it in January 1980 script for the Star Date radio program. She's since moved on to Earth and Sky and set the record straight. But by then this bit of faux folklore had taken on a life of its own.

It's now clear that "Blue Moon" appeared in a 1937 edition of the Maine Farmer's Almanac to denote an extra full Moon in a given season. You're probably familiar with terms like "Harvest" and "Snow" to describe the full Moons at various times of year. But when a fourth one intrudes in the three-month interval between, say, September's equinox and December's solstice, a gap occurs in this naming scheme. That's why editor Henry Porter Trefethen inserted a Blue Moon (as the third of the four) all those years ago in his almanac.

For the numerologists among you, this month's doubletake is the first since May 2007, and the next won't come until August 2012 (there's that scary date again). As for me, if skies are clear when I'm out celebrating, I'll take a peek at that brilliant orb as it rises over the Boston skyline to see if it's an icy shade of blue. Or maybe I'll just howl.