There are events that happen once in a blue moon—but events that happen once in a black moon occur just as often.

This weekend, the world will experience a black moon. The moon itself won’t actually turn black.

The term “black moon” refers to either two new moons in the same month or four new moons in a single season.

The summer of 2025 will have four new moons, and the third of them this season receives the black moon designation.

Black moons are rare occurrences. A new moon happens about every 29.5 days. Since most months are 30 or 31 days long, and a season is roughly 91 days, a black moon usually requires a new moon to fall on the first day of a month or season.

A blue moon happens just as often—when there are two full moons in a month or four in a single season.

One thing that m

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