I just read a post where someone was highlighting the fact that in the year 2018 there were going to be 5 blue moons. A blue moon being defined as two full moons in the same calendar month. I am looking for a research article I did a number of years ago and when I find it I will post it regarding this subject. For now let me just say there is not going to be 5 blue moons this year because modern man has distorted the true meaning of a blue moon. The ancient definition was not two full moons in the same month, but two full moons in the same sign, regardless of the month. And this has not happened since the full moons in May and June of 2016 when both occurred in the sign of Sagittarius. The next true blue moon (which by the way is the name given to the second moon) will not happen again until there is two full moons in March and April of 2019 when they are both in the zodiacal sign of Libra. The April 2019 full moon is the real blue moon. Needless to say, from an Astrological standpoint, when you have two full moons in the same sign, that sign is going to become highly active at that time. It will affect everyone who has that sign prominent in their charts. There are no true blue moons at all in 2018.
I guess you could say true blue moons truly only do come “once in a blue moon”.

Definition of a True “Blue Moon”