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Brian Day's avatar

What fun. I've liked a good calendar deep dive, ever since finally finding out that leap year isn't just "every 4 years", back when working on the Year 2000 problem. This also feels like exactly the sort of entertaining rabbit hole that comes up whenever I look into Passover things, like the first time I participated in the Seder and was deeply confused why Maxwell House Coffee, of all people, published the Haggadah. That's right up there with Michelin Stars and Guinness Book of World Records for advertising pitches that became so culturally fundamental that they transcend sales and actually become somehow "good", which is a pretty wild transformation.

Huh, and I guess actually fits the Easter theme in a weird way.

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The Pachyderminator's avatar

An interesting wrinkle re. the problems in your footnote 11: now that we have atomic clocks, the official clock time is actually more "accurate" (i.e. more mathematically regular) than the solar phenomena themselves, since the earth's rotation is affected stochastically by geological events. Hence "leap seconds" are not added on a fixed schedule, but scheduled as needed by some person in authority (very likely the Astronomer Royal).

(Or were. Apparently leap seconds are difficult for programmers to deal with, and the current plan is to let the error accumulate up to a minute or more and let posterity deal with it. I find this vaguely upsetting.)

However, IIUC, leap seconds are only designed to correct the length of the calendar *day*, not the year. If the Gregorian calendar continues to be used for centuries into the future, some yet-to-be-determined correction will still have to be applied. Per Wikipedia, the 4000-year idea has been proposed before,[1] though I suspect it would make more sense to apply one-off corrections at somewhat shorter intervals, since the 4000-year cycle *still* wouldn't reduce the error to zero, and the length of the cycle is getting a bit ridiculous at that point.

[1] https://en.wikipedia.org/wiki/Gregorian_calendar#Accuracy

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