The Friday’s Full Moon at end the month of August is the second Full Moon of the month, an event known as a “Blue Moon”. The month’s first full moon of the month was on Aug. 1.
The term, “Once in a Blue Moon” has come to refer to something that is extremely rare.
The last blue moon occurred on Dec. 31, 2009.
The next two Full Moons in one month occurs on July 31st, 2015.
This Friday August 31st, the Full Moon occurs at 9:58AM EDT/1:58PM GMT.