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Comment by mbrookes | Hacker News Reader

"once in a blue moon"

That feels like the wrong idiom in this context, just "once in a while" sounds better.

But I couldn't decide why it sounded wrong, so I googled "once in a blue moon". I didn't arrive at a conclusion, but: https://www.google.co.uk/search?q=once+in+a+blue+moon

"once in a blue moon = 1.16699016 × 10-8 hertz"

Huh?!

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I'm a native English speaker. Once in a blue moon, although meaning "very rarely", is fine since I'm using it to say "every so often". But, yes, if we want to nitpick, "which even trips me up very rarely" doesn't sound great. Although, "which even trips me up every so often" does work.

I couldn't figure out at first why it felt off to me as well, but I think you hit the nail on the head. It's not wrong, it's just a little off/unusual.

I figure someone at Google thought it was funny to say that blue moons occur approximately every 1 / (1.16699016 × 10-8 hertz) = 992 days.

http://www.wolframalpha.com/input/?i=1%2F(1.16699016+%C3%97+...

> 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.

Well, it is funny even if true. I searched quickly and found a page that claimed there were 15 blue moons in 20 years so I wasn't sure.

> 1.16699016 × 10-8 hertz

IOW, once every 2.7 years. Google Calculator is genius.

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