Why is the second full moon of a month called “blue?
” The modern definition of a blue moon actually only dates back to the 1940’s. In a question-and-answer column for Sky and Telescope in July 1943, Laurence J. Lafleur of Antiock College quoted the August calendar page of the Maine Farmer’s Almanac where it says “However, occasionally the moon comes full thirteen times in a year.” The almanac reported a blue moon for the month of August that year. Three years later in the March 1946 edition of Sky and Telescope, James Hugh Pruett, an amateur astronomy and frequent contributor, referred to Lafleur’s article, and added to it the comment that “Seven times in 19 years there were-and still are-13 full moons in a year. This gives 11 months with one full moon each and one with two. This second in a month, so I interpret it, was called Blue Moon.” Pruett inferred the definition that a blue moon is the second full moon in a calendar month without referring to the original source, the Maine Farmer’s Almanac-which listed the blue moon occurring on
