General knowledgeAsked by Anonymous from Mountain View, United States1 Oct 2026, 7:50 AM ISTUpdated
In one line
The rarest type of full moon is a Blue Moon.
Full moon — Lunar phase when the Moon is fully illuminated A full moon, which sometimes is a rare Blue Moon if two happen in one month. Image: Wikipedia
The rule
A Blue Moon is when two full moons happen in one calendar month, or the third full moon in a season with four full moons.
Let's understand it simply
Imagine you see a full moon at the start of the month, and then, before the month ends, you see another full moon. That second one is called a Blue Moon. It does not look blue, but it is rare because usually, there is only one full moon each month.
Remember it
A Blue Moon is the rare extra full moon that happens only once every 2–3 years.
Quick recap
A Blue Moon is the rarest type of full moon.
It happens when there are two full moons in one month.
