The name Blue Moon used to indicate something rare. Not anymore! Popular culture has defined several kinds of
Blue Moons. The next one will be in March 31.
In recent years, people have been using the name Blue Moon for two different sorts of moons. The first can be the
second of two full moons in a single calendar month, as with the March 31 Blue Moon. An older definition says a
Blue Moon is the third of four full moons in a single season. Someday, you might see an actual blue - coloured moon.
The Maine Farmer's Almanac defined a Blue Moon as an extra full moon that occurred in a season. One season-winter,
Spring, Summer, fall - typically - has three full moons. If a season has four full moons, then the third full moon may
be called a Blue Moon.
The next seasonal Blue Moom ( third of four full moons in one season) will take place on May 18, 2019.
earthsky.org Feb 24, 2018
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