Question: how often does as blue moon happen on New Year’s Eve?
Answer: once in a blue moon.
A full moon occurs every 29.5 days, and most years have 12. On average, an extra full moon in a month — a blue moon — occurs every 2.5 years. The last time there was a lunar double take was in May 2007. New Year's Eve blue moons are rarer, occurring every 19 years.
The last time was in 1990; the next one won't come again until 2028.