Blue Moon (the second full moon in a month) appeared on July 31 2015 (a little after 8pm ET, although technically it already revealed itself at 6:43am ET).
The next Blue Moon will appear on January 31, 2018. See Blue Moon calendar here.
There are two definitions of a Blue Moon in astronomy; both are a type of full moon. If the moon actually looks blue, it's caused by a rare type of dust in the atmosphere.
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.
See TimeandDate.com's Moon Phase pages to find your local and worldwide times and dates for both of the Blue Moon definitions.
How to see the blue moon: Here's your guide to observing this rare wonder of nature, featured at Mirror.