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2 x 353 = 706-year and 13 x 353 = 4589-year lunisolar cycles

by Karl Palmen :: Rate this Message:

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Dear Irv and Calendar People

Two 353-year cycles is not too bad. I didn't find out about it for some time and have it listed in
http://www.the-light.com/cal/Lunisolar_333.html
It has 257861 days and is formed by combining the primary cycles of 315 and 391 years.
Its mean year is 365.24221 days and mean month is 29.53057719 days.

The cycle of 13 353-year cycles with 1676097 days can be constructed on my lunisolar spreadsheets by setting the number of abundant years (column C) to 891 and is formed from the three primary cycles, by combining six 391-year cycles, two 334-year cycles and five 315-year cycles.
Its mean year is 365.24232 days and its mean month is 29.53058600 days.
As stated in another note by Irv, its mean year is very close to that of the 293-year cycle of 71 leap days or 52 leap weeks.

Karl

10(08(06 till noon

-----Original Message-----
From: East Carolina University Calendar discussion List [mailto:CALNDR-L@...] On Behalf Of Irv Bromberg
Sent: 01 May 2009 02:51
To: CALNDR-L@...
Subject: 13 x 353 = 4589-year lunisolar cycle

Dear Calendar People:

I was unable to find a reasonably accurate intentionally slightly  
short mean month and mean year that yielded an exact integer number of  
days in the 353-year, 4366 lunar month cycle.

Thirteen repeats of that cycle = 4589 years or 56758 lunar months,  
however, can contain exactly 1676097 days (not divisible by 7),  
yielding a mean month of 1676097/56758 = 29+30115/56758 days or 29d  
12h 44m 2+17882/28379s (the fraction is just under 2/3 second) and a  
calendar mean year of 1676097/4589 = 365+1112/4589 days = 365d 5h 48m  
56+1496/4589s (the fraction is just under 1/3 second), or about  
365.242318588 days.

The stable calendar season in the present era is at an ecliptic  
longitude of about 3°, very close to the target northward equinox.

With that mean month, 4366 lunar months (353 years) contains  
128930+7/13 days, so 13 repeats are necessary to make the fraction go  
away (adding up to one week).  In other words, in the full 4589-year  
cycle, 353-year subcycles having 128931 days alternate with 353-year  
subcycles having 128930 days, for a total of 7 + 6 = 13 of the 353-
year subcycles, respectively.

The mean month fraction numerator 30115 indicates it has that many  
full lunar months per cycle, and 56758-30115=26643 deficient lunar  
months.  The difference 30115-26643=3472 is the number of yerms per  
4589-year cycle.  The full 4589-year cycle contains a mix of 61 eras  
of 40 yerms with 24 eras of 43 yerms.

The time unit 1/56758 of a day is just a tad more than 1+1/2 seconds.
Compare with the 1/25920 of day "part" used for the traditional Hebrew  
calendar molad, which is exactly 3+1/3 seconds.

If this 4589-year cycle were used for reform of the traditional Hebrew  
calendar, with a fixed revised molad interval of 29+30115/56758 days,  
then the cycle would nicely approximate the mean northward equinox for  
at least a millennium longer than the 353-year cycle with traditional  
molad interval, but not as long as the 353-year cycle with  
progressively shorter molad interval.  Correspondence with the mean  
lunar cycle would be improved compared to the traditional molad while  
retaining similar arithmetic simplicity, but the progressively shorter  
molad would have much less drift.

-- Irv Bromberg, Toronto, Canada

<http://www.sym454.org/>
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