QUICK! go outside and look UP !!!!! (August 31 )
Each year, the moon completes its final cycle about 11 days before the Earth finishes its orbit around the sun. These days add up, and every two and a half years or so, there is an extra full moon, called a blue moon. The origin of the term is uncertain, and its precise definition has changed over the years. The term is commonly used today to describe the second full moon of a calendar month, but it was originally the name given to the third full moon of a season containing four full moons.