TONIGHT’S FULL MOON WILL BE THE 2nd full moon during this calendar month, the first was on May 2.  Whenever this happens, the second full moon is called the “blue moon.”

How did this name come about?  The phrase “blue moon” dates back to a 16th century proverb:

If they say the moon is blue,
We must believe that it is true.

In other words, it indicated an obvious absurdity.  For a long time the term “until a blue moon comes” meant “never.”  But in more modern times it evolved into “once in a blue moon” meaning “rarely.”

And rarely does the two-full-moon phenomena occur.  The last one occurred on July 31, 2004.  Even more rare, two blue moons occurring in the same year happens once every 19 years or so.  The last time that happened was 1999 in January and March.

Note that these dates are for the Western Hemishere.  In the Eastern Hemisphere (which includes most of Europe) the full moons are a day later…..this year occurring on June 1 and June 30.

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