Once in a Blue Moon

When February has no Full Moon

Several people have noticed that February 1999 has no Full Moon, and have asked me how often that happens.

In 1999, January and March both have two Full Moons. The second Full Moon in January occurs late on the 31st, whilst the first Full Moon of March falls close to the beginning of the month, on the 2nd. You might guess, then, that February has no Full Moon in years when January and March have two Full Moons each. This happens, on average, about three times each century.

But are there any other situations when February misses out on a Full Moon? The answer is: YES.

Years in which February has no Full Moon coincide exactly with those years in which there are double Blue Moons. These may be January-March doubles (the most common) or January-April or January-May doubles. They may also be December-March doubles, such as 1933/1934. Both December 1933 and March 1934 had a Blue Moon, and February 1934 had no Full Moon.

The frequency of double Blue Moons is about 4.5 per century, so this is also the frequency with which February has no Full Moons.