We are fast approaching a blue moon. The event will occur once in a blue moon and the date happens to be August 31, 2012.  It's not that the moon will appear blue, however, it will be the second full moon occuring within the same month. 

It's exciting to enjoy this rare occasion, since a blue moon only takes place about every two and a half years.  When the first full moon takes place at the beginning of the month there is time for a second.  Some also refer to a blue moon as the second full moon within the same season.  Typically there are 12 full moons each year.  One per month. 

Yet in each solar calendar year there are about eleven days more than the lunar year of 12.  The extra days add up so every two to three years we get to enjoy a blue moon.