Re: Date and time on Cindu: yearly update

On Sun, May 18, 2008 at 11:50 PM, ROGER MILLS <rfmilly@...> wrote:
> >You have a purely arithmetic rule about *when* a leap year occurs
>> (years 4, 10, and 17 of a 19-year cycle),
>
> I don't think so: according to my calc. 700 - 706 - 713 - 719 - 725 - 732 -
> 738 etc. were leap years, so it goes 6-7-6.
RIght, those are the intervals between leap years: 6 years, then 7
years, then 6 years.  That means that you have a pattern of leap years
within common years that repeats every  6+7+6 = 19 years; that's the
"19-year cycle" I mentioned.

When I said "years 4, 10, and 17", I didn't mean "4 years, then 10
years, then 17 years"; I meant, "year 4, then skip 6 years to year 10,
then skip 7 years to year 17".  After that, you skip 6 years again,
but the leap-year cycle starts over at 1 after year 19. So from 17 to
18 (1 year) to 19 (2 years) to year 1 of the next cycle (3 years) to
year 2 (4 years) to year 3 (5 years) to year 4 (6 years): 6 years
brings you back to year 4 again, and the pattern of 4, 10, 17 repeats
over and over again.

Those numbers were based on this bit from
http://cinduworld.tripod.com/cindustats.htm: "the last leap year was
751, the next one will be 758."  However, if that's correct, then your
list above is not - if 700, 706, and 713 are leap years, then 758
would not be one; 757 and 763 would be:

     0 |    +6   +7  +6
700  | 706 713 719
719  | 725  732 738
738  | 744  751 757
757  | 763  770  776

So which list do you want to be correct?

> I like that [leap day changing every time] better than having it be a fixed day.
I agree with you there.  Complex is fun. :)

>  (NB I am not skilled at this sort of thing!!!)
That puts you in good company.  JRRT said exactly the same thing in
his description of the Shire calendar. :)

>  I'm still digesting your long previous post..........
I apologize for the length.  Not trying to confuse anyone.  Just
trying to get enough detail to allow me to make a tool for you...

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

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