Re: Date and time on Cindu: yearly update

On Sun, May 18, 2008 at 1:13 PM, ROGER MILLS <rfmilly@...> wrote:
> Their leap days fall nearest whichever equinox/solstice is most out of
> whack.
That's an odd combination, then.  You have a purely arithmetic rule
about *when* a leap year occurs (years 4, 10, and 17 of a 19-year
cycle), but then you place the leap day within that year according to
astronomical observation.  Which makes developing a Cindu converter in
software very hard, by the way!  But the point is it would be more
consistent, at least to human logic, if you used either astronomy or
arithmetic for both, i.e. "a leap year occurs whenever any of the
equinoxes or solstices is off by more than a day" .

On Earth, that rule would be problematic because the equinoxes and
solstices move relative to each other in ways that make it impossible
to correct for all of them; you have to pick one to go by.

Alternatively, and this is what I would recommend as a programmer
implementing the conversion, you could fix the leap day according to a
simple rule.  e.g. "the leap day is always the day before the spring
equinox" or "each leap day occurs a quarter later than the last leap
day" (the specific date chosen according to your waiting/dancing rule,
of course).

> They are holidays and unnumbered, and create long "weekends"--
> and every month begins on lembrim 1.  Does that make sense? Any more or less
> sense than assigning ours to February 29?
More sense, I'd say.  The choice of February is historical; the old
Roman calendar began with March, so February, as the last month of the
year, was a logical place to put extra stuff.  On the other hand, they
still did it weirdly, inserting the extra month *inside* February,
splitting it in two parts...

Random calendar trivia: the traditional leap day is not February 29th,
but the 24th or 25th, depending on whom you ask.  The way the Romans
counted the dates, after February 13th (the Ides of February, slightly
less famous than the one a month later), you start counting down to
March: Feb 14th = xvi, 15th = xv, 16th = xiv, 17th = xiii, etc. (If
the math seems off, that's because the actual Kalends of March, March
1st, was counted as i, not zero, since the Romans didn't have the idea
of zero as a number yet. Or a way of writing it in Roman numerals. :))

In leap years, you might expect that, those numbers would just go up
by one, starting with Feb 14th = xvii. But 'tweren't so.  Instead, the
days from Feb 14th through the 2rd got the same numbering they got in
common years, xvi through vii. But the 24th and 25th were both labeled
vi, one of them being counted as a "second sixth" day (Latin. "bis
sextum"  => modern technical term "bissextile", which means "leap" in
the calendar sense).

Sources differ on whether the 24th or the 25th was the "second" day
vi, and therefore the traditional "leap day", what with the whole
counting backward and all.

--
Mark J. Reed <markjreed@...>

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