The month of August will bring us two full moons. Usually a full moon occurs only once in a month, when two full moons occur within a calendar month, the second full moon is called a “blue moon”. But remember that a blue moon is simply the second full moon in month. It doesn’t actually have anything to do with color at all.
The first full moon will be kicked off on Wednesday, August 1, and the second full moon will be witnessed on August 31 which will be a ‘blue moon’. The origin of the calendrical term “blue moon” was discovered in the year 1999.
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 there is an extra full moon called blue moon. Since the blue moon occurs every two or three years, the phrase “once in a blue moon” came into existence which refers to occurrences that are uncommon, though not truly rare.
The next time two full moons in a single month come in July 2015 (July 1 and 31).