出典:Wiktionary
blue moon (countable かつ uncountable, 複数形 blue moons)
出典:Wikipedia
出典:『Wikipedia』 (2011/07/15 17:08 UTC 版)
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.
blue moon
the blue sky
青空.
the blue sky
a halo encircling the moon
the gibbous moon
月.
the moon
the moon
the waning moon
the appearance of the moon