Old Earth Calendar

[Irv Bromberg]

On Apr 21, 2006, at 07:41, Palmen, KEV (Karl) wrote:
> IRV CONTINUED:
> The day-wise epoch adjustment also doesn't work for the Symmetry454
> Calendar or essentially ANY leap week calendar because at the epoch the
> first calendar year was constrained to start on the calendar's starting
> weekday.
>
> KARL SAYS:
> I don't really understand what Irv means here about day-wise
> adjustment in this context.

IRV ADDS:

Although small integer epoch shifts are generally applicable to any
leap DAY calendar, that would not be the case for a perpetual leap day
calendar where the weekday that start the year is constrained.  Thus,
for example, The World Calendar and the 13-Month Calendar are
constrained to start the calendar year on Sunday, and for these a small
integer epoch adjustment could not be used to adjust equinox alignment.
  This is the same constraint that applies to a leap WEEK calendar.

I am working on a uniformly-spread leap DAY variant of the Bahai
Calendar, which will use the leap day equivalent of the selected Sym454
leap rule in Kalendis, starting the year on the day on which FLOOR( New
Year Moment + Haifa meridian offset ) lands.  As this calendar has no
constraint regarding the starting weekday at the epoch, if necessary
the equinox could be aligned to land on the New Year Day by shifting
the epoch.  However, the Sym454 leap rules are tuned to the Prime
Meridian, so even when including the Haifa meridian offset I don't
expect the equinox alignment to be centered with respect to the Bahai
New Year Day, and an integer epoch shift won't fix that.  If the Bahai
somehow became seriously interested in this approach, then they would
want the equinox to be centered.  Not likely -- after more than 3/2
century they still haven't selected one equinox reference meridian.

I have searched on many occasions for official information about the
Bahai Calendar at <www.bahai.org>, but never found a shred of
information, leading me to believe that the Bahai play down their
innovative calendar.  Recently, however, I followed a link from
Wikipedia's Bahai Calendar page to a single calendar related page and
PDF at the US Bahai web site, which apply only to the Western Bahai
Calendar that starts the year on Gregorian March 21st:

<http://www.bahai.us/content/view/31/96/>
<http://www.bahai.us/images/files/BahaiCalendarOptimized.pdf>

One gets the disappointing impression from the above web page that the
Bahai have no interest in calendrical calculations for their innovative
calendar, nor any reforms of it.  The PDF gives one the strong
impression that the US Bahai use their calendar merely as a way to
relabel the Gregorian Calendar.  Its month names, which probably seem
strange to any who are not of the Bahai faith, and are reminiscent of
the earlier French Revolutionary Calendar, seem to tie to
theme-of-the-month social programming.  It looks as if the Bahai simply
find the month that starts at the day that is closest before the given
Gregorian Calendar date, then count up to 19 days from there to get the
Bahai Calendar date.  Furthermore, the US Bahai have two holidays that
are stated in terms of the Gregorian Calendar only, and cannot be
expressed in terms of a rule that would apply to the Bahai Calendar:

World Religion Day = 3rd Sunday in Gregorian January
Race Unity Day = 2nd Sunday in Gregorian June

(both of the above move around between two adjacent Bahai months)

It is, however, neat that the Bahai intercalated days span Gregorian
Feb 29th, so that ALL Western Bahai Calendar months have permanently
fixed starting dates on the Gregorian Calendar, as shown on the PDF
linked to above.

I have not seen Bahai Calendar arithmetic documented anywhere other
than the Reingold & Dershowitz book, "Calendrical Calculations:  The
Millennium Edition".  The R&D Bahai algorithms depend excessively on
the arithmetic of the Gregorian Calendar rather than using
self-contained Bahai arithmetic when possible, so I have developed my
own Bahai arithmetic.  Thus my planned web site will give my arithmetic
for the Western Bahai Calendar, along with uniformly spread leap day,
leap week, and leap month variants (just to confuse everybody).  The
leap day or week variants could also be used for implementing the
"Future" Bahai Calendar, as R&D call it, an astronomical calendar tied
to the northward equinox, by selecting the NE79 leap rule from the
Symmetry454 arithmetic and including a New Year offset for a specified
meridian.  Once this is all compiled and posted, I fully expect the
Bahai to ignore it, for the reasons given above!  Therefore I am
considering renaming these as "BIC" variants ("Bahai-Inspired
Calendars").

I wonder if there is effective treatment available for the
"unable-to-stop-working-on-an-utterly-futile-calendar-project"
syndrome?

Back to the thread "Egyptian leap month variant", which Karl chose in
reference to a 30-day leap month calendar because an ancient Egyptian
Calendar had 12 months of 30 days (plus presumably some intercalary
days).  It is worth pointing out that the French Revolutionary Calendar
was very similar, being based on twelve 30-day months plus 5
"Revolutionary" days (6 in leap years).  So the 30-day leap month
variant could be called a leap month variant of the French
Revolutionary Calendar.  Its 10-day weeks would not be a "hit",
however, and if it were to tie to the southward equinox then a leap
month adaptation of my LASEY progressive leap rule would be necessary.  
Actually the LASEY arithmetic would be unchanged except that the New
Year Moment would be either FLOORed or ROUNDed to the nearest or
nearest prior modulo-30 ordinal day number since the calendar epoch.  
LASEY is documented at <http://www.sym454.org/leap/>.

-- Irv Bromberg, Toronto, Canada

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