The Rare Blue Moon - How to Take Advantage of This Special Event

The expression 'Once in a Blue Moon' is used to express a rare and often special event. This is because a Blue Moon occurs just once in every two and half years or so. This special Moon occurs when a second full Moon falls in any one calendar month. Usually months have only one full Moon, but occasionally there can be a second one - named a Blue Moon.

Full Moons occur every 29 days, but most months are 30 or 31 days long; so it is possible to fit two full Moons in a single month. This happens rarely. The last Blue Moon was December 31 2009, and the next is August 31 2012. After that you'll have to wait until July 31 2015 for the next one.

The Moon phases are seen as important for many established and traditional religions, often marking special significant dates in the religious calendar.

Both the Islamic calendar and Jewish calendar are lunar. Christianity sets its most important event of celebrating Easter on the first Sunday following the first full Moon after the Spring Equinox. Buddhism, Sikhism, Hinduism and Jainism also follow the Moon cycles to mark significant festivals.