Monday, December 5, 2011

Once in a Blue Moon!!

A blue moon can refer to the third full moon in a season with four full moons. Most years have twelve full moons that occur approximately monthly. In addition to those twelve full lunar cycles, each solar calendar year contains roughly eleven days more than the lunar year of 12 lunations. The extra days accumulate, so every two or three years (7 times in the 19-year Metonic cycle), there is 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.
In calculating the dates for Lent and Easter, the Clergy identify the Lent Moon. It is thought that historically when the moon's timing was too early, they named an earlier moon as a "betrayer moon" (belewe moon), thus the Lent moon came at its expected time.



Folklore gave each moon a name according to its time of year. A moon that came too early had no folk name, and was called a blue moon, retaining the correct seasonal timings for future moons.
The Farmers' Almanac defined blue moon as an extra full moon that occurred 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.

A "blue moon" is also used colloquially to mean "a rare event", reflected in the phrase "once in a blue moon".




Here's a Blue Moon Calendar
1950-1999 | 2000-2050

--------------------+--------------------
May 31, 1950 | November 30, 2001
December 31, 1952 | July 31, 2004
October 31, 1955 | June 30, 2007
July 30, 1958 | December 31, 2009
January 31, 1961* | August 31, 2012<--- next
April 30, 1961* | July 31, 2015
November 30, 1963 | January 31, 2018*
August 31, 1966 | March 31, 2018*
May 31, 1969 | October 31, 2020
December 31, 1971 | August 31, 2023
October 31, 1974 | May 31, 2026
July 30, 1977 | December 31, 2028
March 31, 1980 | September 30, 2031
December 30, 1982 | July 31, 2034
July 31, 1985 | January 31, 2037*
May 31, 1988 | March 31, 2037*
December 31, 1990 | October 31, 2039
September 30, 1993 | August 31, 2042
July 30, 1996 | May 30, 2045
January 31, 1999* | January 31, 2048
March 31, 1999* | September 30, 2050

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