Why does the Supermoon Blue Moon, which comes ‘once in a decade’, happen twice in 2 years?

Science: When is the next supermoon blue moon?

As we prepare ourselves for the rise of the supermoon blue moon on Monday, August 19 at 2:26 p.m. EDT (1826 GMT), some of you sharp-eyed readers may ask “Wait a minute, during last year’s supermoon blue moon you said the next supermoon blue moon would be in 2037, thus making it a once-in-a-decade event?” and you’d be right, well… it’s complicated.
The term “blue moon” actually has two meanings, so they’re not as rare as you might think, so so much for “once in a blue moon,” right?
The seasonal blue moon is the traditional definition of a blue moon and refers to the third full moon in a season with four full moons, according to NASA. The other definition — which arose from a misunderstanding of the origin — is the monthly blue moon, which refers to the second full moon in a calendar month. Today, this monthly blue moon is accepted as an alternate definition rather than a mistake, according to Time & Date.

Supermoon is more common and means any full moon that occurs when the moon is within 90% of its closest point to Earth, according to NASA. This year there will be four consecutive supermoons: Aug. 19, Sept. 17, Oct. 17 and Nov. 15. The closest supermoon of 2024 will be on Oct. 17 at 7:26 a.m. EDT (11:26 p.m. GMT).

So the next supermoon blue moon according to the monthly blue moon definition will actually be on Jan. 31, 2037, at 10:03 a.m. EST (1403 GMT).

But the next supermoon blue moon according to the seasonal blue moon definition will be on Aug. 19, 2024, at 2:26 p.m. After 1826 EDT (1826 GMT), we won’t see another supermoon blue moon (under the seasonal definition) until August 20, 2032.

After Monday’s full moon, we’ll have to wait at least 8 years for the next supermoon blue moon, so if you can, try and get out and see it shine! The moon will also appear full on the nights before and after August 19.