Whats A Blue Moon

Kids Learning

Have you ever heard anyone say something only happened “once in a blue moon”? Did you know what they meant?

A “blue moon” is when one month of the year has two full moons in it, like January of 1999 which had a full moon on January 1 and another on January 31.

Because the phases of the moon usually only result in one full moon each month, a “blue moon” month with two full moons is a pretty special thing. That’s why people say something happens “once in a blue moon.”

Now, if one blue moon a year is special, think about this. The year 1999 had a blue moon in January, but it will have another blue moon in March because there will be full moons on March 2 and another on March 31.

Experts say that two blue moons in one year happens about every 19 years, so two blue moons in one year is really something that happens once in a blue moon!