Subj : Re: Daylight Savings
To   : Ed Vance
From : Adept
Date : Tue Mar 25 2025 06:22 pm

 EV> By what I can figure out, our Earth orbits around the Sun in 365.26 Days.
 EV> When I attended Elementary School I was told Spring always starts on
 EV> March 21 each year.
 EV> Now Spring begins on March 20.
 EV> Makes Me wonder because Earth's orbit has an extra 1/4th Day how long it
 EV> would take when Spring begins on March 19?

Evidently it'll happen in 2028. If you're in Chicago, but not if you're in Germany.

That said, this is the reason for having a leap day, and for eventually skipping leap day in the divisible-by-100 year, but not the divisible-by-400 year.

But, e.g., Chicago has these times, for Spring equinoxes:
2025 - 3/20 04:01
2026 - 3/20 09:45
2027 - 3/20 15:24
2028 - 3/19 21:17
2029 - 3/20 03:01
2030 - 3/20 08:51
2031 - 3/20 14:40
2032 - 3/19 20:21

Had we skipped leap day in 2000, it'd still mostly be on the 21st, with going to the 20th every 4 years.

But we creep forward about an hour on the calendar every 4 years, with the leap day included.

Thus why it takes about 24 of those cycles for it to be reasonable to skip a leap day. That's not quite 25 (and thus a century), and I'm guessing it's probably actually about 22 cycles. That said, that's just me going backwards on the math and assuming the people who made the calendar had the right ideas, for why we have leap days when we do.

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 * Origin: Storm BBS (21:2/108)

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