On Tuesday night at 6:45 p.m., the moon was officially full -- and it was "blue."
The full moon was a blue moon based on the technical definition: it was the third full moon in a four-full-moon season (winter, spring, summer and autumn).
The more common term for "blue moon," referring to when two full moons occur in one month, was due to some confusion caused decades ago by Sky and Telescope magazine as it was trying to interpret information from the Maine Farmers' almanac of 1937.
After last night's full moon, another blue moon will not occur again until 2015.
SLIDE SHOW: Check out some beautiful photographs of this year's blue moon from KING 5 viewers.
For more interesting facts about the blue moon, read NBC News's article.