We've all heard the phrase "once in a blue moon", and many of us think we know where it comes from. Well, it seems that most of us, myself included, don't have all the information. Depending on which definition you use, you're either going to experience a new moon this month, or you'll have to wait until next year. So why all the confusion?
How do you know which full moon is a blue moon? In a recent thread in the Pagan Blog Project Group on Facebook, Rowan Pendragon, who created that project, told me, "A true Blue Moon occurs when there are four full moons in a single season." In such a season, it's the third full moon which is considered blue, although she didn't mention that part, and when asked how to determine seasons said, "By the solstices and equinoxes. This is taking the actual date of the seasonal change into account to mark the start and end of the season."
I felt the urge to look into it further because my brain likes solving little puzzles like, what are the origins for the idea of a blue moon and what is it. The most common explanation anyone will give if asked what a blue moon is tends to go something like, "the second full moon in a given month." However, it turns out that this understanding of blue moons, not moons actually appearing blue in color, that's something else entirely, came about from a misinterpretation or misunderstanding! While researching for an article, James Hugh Pruett read copies of the Maine Farmer's Almanac which contained references to a blue moon. However, the system for figuring out when one occurred was complicated involving the seasons and a different calendar called a tropical year, which goes from one winter solstice to the next.
Here is where the confusion sets in. Using a standard calendar, and relying on solstices and equinoxes doesn't line up the same as using the tropical year method used in the almanac, which is where this whole thing really started from because the only other references to blue moons I've been able to dig up are in a 1524 pamphlet filled with hate speech aimed at the English clergy, which possibly eludes to the betrayal of council from a religious person (i.e. going against the religious order on matters only rarely happening). That may kind of line up with 'blue moon', but doesn't apply to the seasonal/cyclical use of the term.
How does all of this fit into the modern context of Pagans? While I don't personally see a magickal significance to the blue moon vs another full moon, it's certainly a bonus time for any workings you normally do during that time! In my opinion, the seasonal method makes sense from a Pagan perspective since so many of us are already referring to some form of the Wheel of the Year already. I also pay attention to seasons and natural cycles because I'm a gardener. I'm not going to rob my friends, who will be experiencing the blue moon of 2012, of any joy by trying to tell them which moon is "truly" blue because it's now clear to me that is just plain silly; ultimately, it appears to be a fairly modern fabrication in the sense we use it in the real world, although it was interesting to learn the origins of its use in language.
1 Farmers Almanac http://www.farmersalmanac.com/astronomy/2009/08/24/what-is-a-blue-moon/
2 Koelbing, Arthur, Ph.D. (1907–21). "Barclay and Skelton: German influence on English literature". The Cambridge History of English and American Literature, Volume III.