Friday is the last blue moon until 2018
WEATHER.COM — It’s almost time for another blue moon, but we’re not talking about a drink. In most cases, the term describes the phenomenon that takes place when there are two full moons in the same calendar month. According to Earth Sky, the next blue moon will occur on July 31.
Generally, the moon is only full about once every 30 days. This means the blue moon phenomenon can only take place if there is a full moon in the first few days of a month. The last full moon was on July 2.
The phenomenon occurs once every two or three years. The last one took place on Aug. 31, 2012. After this month, there won’t be another Blue Moon until 2018, according to the Orlando Sentinel.
A blue moon is an additional full moon that appears in a subdivision of a year, either the third of four full moons in a season or, a second full moon in a month of the common calendar.
The phrase has nothing to do with the actual color of the moon, although a literal “blue moon” (the moon appearing with a tinge of blue) may occur in certain atmospheric conditions; e.g., when there are volcanic eruptions or when exceptionally large fires leave particles in the atmosphere. This phenomenon is specific to calendars. Lunar calendars like the Indian national calendar always have one full moon a month.