What Is A Blue Moon?

What Is A Blue Moon?

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Story Published: Jul 15, 2004 at 10:49 AM PST

Story Updated: Mar 13, 2008 at 12:13 PM PST

By Steve Pool

SEATTLE - You've likely heard that something might happen just "once in a Blue Moon" but just how often is that? Well, there's one this month: July 2004 will feature a Blue Moon.

A Blue Moon is the term given for the rare occasions when we have two full moons within the same month -- it's the name for the second full moon.

Since full moons come about every 29 1/2 days, you can see it's hard to squeeze two in a month. But it happens about every 2 1/2 years.

And talk about 'once in a blue moon', in 1999, there were *two* Blue Moons -- one in January, and another in March. That occurs every 19 years or so.

This month, we'll have full moons on July 2 and 31. And no, the moon does not actually turn blue.

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