Today, November 21 marks Blue Moon. This is called the Long Night Moon, or the Moon Before Yule. When there was a large volcanic eruption from Mount Pinatubo in the Philippines in 1991, the moon was blue. Today's full moon falls on Sunday November 21 and the third full moon in the last quarter which means it is officially a Blue Moon. It'll be the only full moon this November 2010.
The term Blue Moon been given by the Sky and Telescope magazine in an issue from 1946. James Hugh Pruett wrote in article (Once in a Blue Moon) in which he talked about the blue moon where he spoke on the same magazine article which talked about the same subject. He said that if there are seven blue moons in 19 years, then there are 13 full moons every year.
Blue Moon has its meanings. A Blue Moon maybe the second full moon in a calendar month. Or maybe the third of four full moons in a single season.
