The Blue Moon
What is a Blue Moon?
_ The Farmers' Almanac defines a blue moon as an extra
full moon that occurs in a season; one season was normally three full
moons. If a season had four full moons, then the third full moon was
named a blue moon. Most years have twelve full moons that occur
approximately monthly. However, since the lunar cycle has less days than
the solar calendar year, every two or three years those days accumulate
and result in an extra full moon.
Lunisolar calendars have rules about when to insert such an intercalary or embolismic ("leap") month, and what name it is given; e.g. in the Hebrew calendar the month Adar is duplicated. The term "blue moon" comes from folklore. Different traditions and conventions place the extra "blue" full moon at different times in the year. |
Next Blue Moon:
July 31, 2015 Blue Moons After: January 31, 2018 March 31, 2018 October 31, 2020 (dates based on EST) |