Rare blue moon appears Friday

The last time a blue moon happened was on New Year's Eve 2009. The next blue moon will occur on July 31, 2015, according to moongiant.com. The phrase "blue moon" has been around for more than 400 years, writes Philip Hiscock, a folklore expert at the Memorial University of Newfoundland, in an exhaustive piece on the origin and uses of the term "blue moon." Read more: Tonight's blue moon won't be seen again until 2015