Full Moon

Vin tells me it was a blue moon which surprised me because it wasn't very late in August. But I learned something new.

This usage of the term "blue moon" to describe the second full moon in one calendar month results from a misinterpretation of the traditional definition of that term in the March 1946 issue of Sky & Telescope. Before then, the term was used to describe the third full moon in a season with four.