Mark your calendars, we humans will be witnessing one of the rarest types of moons, the Blue Moon.

This Halloween, we will be witnessing the first Blue Moon in the last 2 years and 6 months.

On October 1, 2020, the first full moon will happen and the second one will happen on October 31, 2020, which is just right for the Halloween. This means that along with Halloween this year, we will be witnessing the extremely rare Blue Moon.

According to NASA, Blue Moons, which are not blue in color, happen every 2 and a half to 3 years.

Full moons are not rare, but blue moons are, this is why we have the term “once in a Blue Moon”.

A Blue Moon is a rare phenomenon that involves the appearance of an additional full moon within a given period. This type of moon happens every 2.5 years, says NASA.

The term Blue Moon has been applied to the second full moon within a single calendar month, this means that there are around 29.5 days between full moons, making it unusual for 2 full moons to fit into a 30 or 31 day long month.

As you may have guessed it, the month of February will never have a Blue Moon.

Sorry February, you’re just different.

If you’re still confused, just read.

There are 2 ways of calculating the date of a Blue Moon, which are:

1. Seasonal Blue Moon = the third Full Moon in an astronomical season with four Full Moons (versus the usual three).
2. Monthly Blue Moon = the second Full Moon in a month with two Full Moons.

Between 1550 and 2650, there are 408 seasonal Blue Moons and 456 monthly Blue Moons. Either Blue Moon will occur roughly every 2 to 3 years.

Seasonal ones are rarer.

The upcoming blue moon is a monthly blue moon, but it is still rare.