Yes, there really is such a thing as a “Blue Moon”, just ask NASA!
From NASA.gov: “According to modern folklore, a Blue Moon is the second full moon in a calendar month. Usually months have only one full moon, but occasionally a second one sneaks in. Full moons are separated by 29 days, while most months are 30 or 31 days long; so it is possible to fit two full moons in a single month. This happens every two and a half years, on average.”
We had our first full moon of July on July 2, 2015 – and we’re going to see a second full moon (a Blue Moon) this month on July 31, 2015.
The relative rarity of this phenomenon is the origin of the common phrase “Once in a Blue Moon”. According to our research (the NASA website), the same exact thing happening Blue Moon in July 2004.
Learn more cool Blue Moon Facts on MoonGiant.com.