It's a Blue Moon on August 31st! What's a Blue Moon? It's a Blue Moon, according to Wikipedia, if it's "the third full moon in a season with four full moons, or the second full moon in a month. Most years have twelve full moons that occur approximately monthly. In addition to those twelve full lunar cycles, each solar calendar year contains roughly eleven days more than the lunar year of 12 lunations. The extra days accumulate, so every two or three years (7 times in the 19-year Metonic cycle), there is an extra full moon." It's a Blue Moon tomorrow but you may appreciate the Elvis Presley rendition of "Blue Moon," even more than the science. It's Elvis taking you back to 1956 with Blue Moon! You can take in full science@NASA Blue Moon coverage below the fold.