The next Blue Moon is scheduled to appear on January 31, 2018. View Blue Moon calendar from 2012 to 2042 here.
In astronomy, a Blue Moon is a full Moon, which doesn't quite fit in with the months in our calendar. However, there are two completely different ways of calculating which full Moon is a Blue Moon.
Two definitions:
- Blue Moon = The third full Moon in an astronomical season with 4 full Moons (versus the normal 3)
- Blue Moon = The second full Moon in a month with two full Moons.
The correct, original definition is that a Blue Moon is the third full Moon in an astronomical season with four full Moons. A normal year has four astronomical seasons - spring, summer, fall (autumn), and winter - with three months and normally three full Moons each.
When one of the astronomical seasons has four full Moons, instead of the normal three, the third full Moon is called a Blue Moon.
Learn more facts about Blue Moon at TimeandDate.com.
Tip! Find out how to see the Moon with Space.com's telescope viewing tips.