Due to the moon's cycle being 29½ days, there are occasionally - as in July 2004 - two full moons in one month (only happens on average every 2.7 years). Then the second moon of the month is called a "blue moon." (From new-age.co.uk)The older, Farmer's Almanac definition of a blue moon is the third full moon in a season that has four full moons. Don't think too hard about that one, it's kind of roundabout ... then again what do you expect from the Farmer's Almanac on the topic of full moons?
Over the next 20 years there will be about 15 blue moons, with an almost equal number of both types of blue moons occurring. No blue moon of any kind will occur in the years 2011, 2014, and 2017. (From infoplease)A double blue moon -- that is two blue moons in one year -- occurs every 19 years. In 1999 there was a blue moon in January and March. And, if you didn't want to do the math, the next time we'll have fourteen full moons in one calendar year is 2018.
Given these kind of numbers you'd think that a blue moon falling on New Year's Eve would be extremely rare. I was willing to bet on it occurring once every fifty or hundred years. Nope. According to The Atlantic the last one happened in 1990.
The phrase "blue moon" has been traced as far back as 1528 to a work by William Barlow: Treatyse of the Buryall of the Masse
"Yf they saye the mone is belewe,Or, if you're a little rusty on your pre-standardized spelling English:
We must beleve that it is true."
"If they say the moon is blue,No idea what that means.
We must believe that it is true."
In the 19th century until a blue moon meant the equivalent of when pigs fly. It has since morphed into once in a blue moon meaning rarely.
Meanwhile, the mice from Babe sing:
[I had to snag the video off of the movie trailer and then edit it down to just the mice/credits. They sing a little bit longer in the film but not much.]