Answer: February

Every once in a blue moon, if you’ll pardon the pun, the Moon skips its monthly appearance. It still completes a full lunar cycle, mind you, but thanks to a bit of mathematical sleight of hand, the Moon doesn’t make an appearance in the month of February.

February is the shortest month sporting only 28 days in a common year (29 days in a leap year) and the lunar cycle is roughly 29.5 days long. As such, it’s possible for the lunar calendar and our calendar to align in just such a way that the full moon makes no appearance in the month. In fact, this alignment occurs about once every 19 years.

For example, in the Americas (time zones are important to how the Moon’s visibility aligns with the calendar on a given night) there was no full moon in February of 1999 and 2018. The next time we’ll see that alignment again is in 2037.