According to the rule of astronomy, a Blue Moon is defined as the second full moon occurring during a calendar month but a somewhat obscure rule allows us to call it a Blue Moon, Discovery News reported.
The fact is that the current one month" rule has surpasses the rule that allows us to call Tuesday's full moon 'blue.'
On the 1937 Maine Farmers' almanac (not same as The Farmers' Almanac that is still being published in Lewiston, Maine) page, the Blue Moon's definition stated that occasionally '1 of the 4 seasons is going to feature four full moons instead of the usual three.
The almanac further read that there are 7 Blue Moons in a Lunar Cycle of nineteen years, explaining that in the olden times the almanac makers had difficulty while calculating the occurrence of the Blue Moon and this was the uncertainty that gave rise to the expression 'Once in a Blue Moon.'
Back in the July 1943 issue of Sky and Telescope magazine, Lawrence J. Lafleur in a question and answer column quoted the Almanac's account but never specified any date for the Blue Moon.
It turns out that, in 1937, the Full Moon occurred on Aug. 21, which was the third full moon in the summer of 1937, a summer season that would see four full moons.
But the 'two full moons in a month is a Blue Moon came into being because of author James Hugh Pruett, made a reference to the term 'Blue Moon' in his article in Sky and Telescope and referenced LaFleur's S and T article from July 1943.
But as Pruett did not have any specific dates to fall back on, his interpretation was highly subjective and he came to the conclusion that seven times in 19 years there were - and still are - 13 full moons in a year, which gives 11 months with one full moon each and one with two. This second in a month, so he interpreted it, Blue Moon.
Pruett's explanation was, of course, wrong interpretation and it might have been forgotten had it not been Deborah Byrd who used it on National Public Radio program, StarDate on Jan. 31, 1980.
After the radio show, the incorrect Blue Moon rule 'went viral.'
--ANI (Posted on 21-08-2013)