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Why do we have leap days?

28 Feb 2020, 14:00 UTC
Why do we have leap days?
(200 words excerpt, click title or image to see full post)

Note 1: Tomorrow is leap day! February 29, 2020. And I am nothing if not frugal (or at least marginally lazy): This article is a slightly edited version of the same one I posted in 2008, 2012, and 2016. You may notice a pattern. I expect I will continue to do so up until 2200, for reasons that will become apparent as you read, assuming I'm still alive and not locked in a stasis pod somewhere.

Note 2: This post has math in it. Quite a bit. But it's really just arithmetic; decimals and multiplication. If you're a numerophobe, then skip to the end, but you'll have to trust me on the numbers.

If you're a numerophile and a pedant, then you may fret over my somewhat contemptuous handling of significant digits below. But in this case the mantissa (the collected numbers to the right of the decimal point) is what's important, since those are what cause all the leap day grief in the first place. If I carried that out too far it would make this whole mess quite a bit messier, so I kept all the numbers to four decimal places (unless they end in 0), and ignore ...

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