03/05/1998 AT 12:00 AM EST

A blue moon, Sunday. Another blue moon will be coming on the night of March 31. The term "blue moon" refers to the infrequent occurrence of two full moons in the same month, which usually happens roughly once every 33 months.Two blue moons in one year happens every 20 to 40 years. The last time was in 1961.

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