Today will be one of those days that is "once in a blue moon." To be more accurate, a so-called "blue moon" occurs when a month includes two full moons.
Skywatchers say this could be one of the last chances to see a blue moon for nearly three years. The moon reaches its full phase today, marking the second full moon of August. Stargazers won't be able to see two full moons in a single month again until July 2015.
The phrase "once in a blue moon" dates back to 1824.