Describing the blue moon
The term “blue moon” in this context has nothing to do with the moon’s appearance. The practice of referring to the second full moon as a “Blue Moon” if there are two full moons in the same month dates back to the year 1940. On this day, the moon will appear enormous and bright but not blue because it is also a supermoon.
How frequently do blue moons take place?
This occurs only sometimes. A full moon happens every 29 days on average. As most months have 30 or 31 days, a month may occasionally have two full moons. The average frequency of that once every two and a half years. Unusually, there were two blue moons in 2018 that were separated by just two months, one of which was a lunar eclipse! A blue moon and a super moon will occur on the same night once more between January and March of 2037, which is another 14 years from now. This occurrence occurs around every 10 years.