The magazine acknowledged the error in 1999 (with the help of Hiscock and astronomer Donald W. Olson) but, by that time, the new definition had already won out over the old.
In a light-hearted press release issued by the magazine this week, Kelly Beatty, Sky & Telescope's senior contributing editor, said, "In modern usage, the second full moon in a month has come to be called a 'Blue Moon.' But it's not! This colorful term is actually a calendrical goof that worked its way into the pages of Sky & Telescope back in March 1946, and it spread to the world from there."
Sticklers might point out that according to the former definition, there is no blue moon to be had this month. The next one won't happen until Nov. 2010.
But those who subscribe to the old meaning are in the minority.
"Usage has just sort of driven it to be the way it is now," said Alan MacRobert, senior editor of Sky & Telescope. Language shifts and evolves and, especially when it comes to the moon, "you can't beat back the tide," he quipped.