> I figure someone at Google thought it was funny to say that blue moons occur approximately every ... 992 days.

Not sure if your comment's implying it's a random number picked for amusement? That figure (2.7 years) seems about right to me -- the frequency of a blue moon is necessarily the same as the frequency that a lunisolar calendar has to add a leap month, which is every 2 or 3 years. I don't see any reason to doubt Google's number.