The night of July 31st is the night of the Blue Moon, but that is not that rare an occasion. Although, we use the idiom to prove how rare certain things are, but in reality the subject of the idiom is not at all a rare instance, at least not by cosmological means.
According to the astronomers, a Blue Moon is to a great deal a relative occurrence in a time span of around about two to three years.According to an Astronomer, Jacqueline Faherty, the idea of a night with a blue moon is completely relative to a lot of things.
The fairy tales suggests the night of the Blue Moon to have a sky filled with blue light from the moon, but sadly, things are just as normal as on any other night of a full moon. The Blue Moon is actually referred to the full moon that comes out for a second time during the month of Harvest in a year.
The Blue Moon has quite a few legends related to it, but without any substantial connections. The first full moon this month was on 2nd July and 31st July has the second full moon. The completion of the Lunar Cycle of 29.5 days a bit early leads to the Blue Moon.