Tonight there will be a “blue moon,” which is the name for the second full moon in a month. (The first full moon this month was December 2nd and the second will be tonight, on December 31.) The name does not refer to the moon’s color but reflects the rarity of the event and gives rise to the expression, ‘‘once in a blue moon.’’
The Blue Moon of 1982 was even more special because a total lunar eclipse also occurred (for the United States) then.
The last time there was a blue moon on New Year’s Eve was in 1990, and the next one will be in 2028. Blue moons in general are not frequent. The next scheduled times are:
2012: August 2, August 31
2015: July 2, July 31
The rare phenomenon of two blue moons (using the more recent definitition) occurring in the same year happens approximately once every 19 years. 1999 was the last time a blue moon appeared twice, in January and March. The months of the double blue moons are almost always January and March. That is because the short month that falls in between them, February, is a key ingredient in this once-every-19-year phenomenon. For January and March to each have two full moons, it’s necessary for February to have none at all. Since February is usually 28 days long, and the average span between full moons is 29.5 days, if a full moon occurs at the end of January, it’s possible for the next full moon to skip February entirely and fall in the beginning of March.
Happy New Year’s Eve!!!