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August 2013 blue moon

Photo of the August 20, 2013 blue moon by Facebook user Gillian Floyd near Toronto, Ontario.

Blue moon rising

On August 20, 2013, we saw a blue moon rise over planet Earth -- but despite what many may think, it isn't actually blue. The name is given to the second full moon in a calendar month, a relatively rare occurrence. The name is also used to refer to the third full moon in a season with four full moons. You can read more about both in our Geekquinox blog.