[net.religion.jewish] Algorithm for Calendar Date of Jewish Holidays?

greg@sdcsvax.UUCP (Greg Noel) (09/27/84)

Y'shana Tova.  (Did I spell that right?)

I have been working on a program that keeps track of fixed, regular
events and allows you to display them.  For those of you who have
used it, it is a C version of the PDP-10 "LESCAL" program.  It uses
a file of dates that you consider interesting, and has various ways of
specifying dates so that "second tuesday" and the like can be given.
It also has a number of "special-algorithm" dates for calculating
things like President's day, bi-monthly paydays, and Easter.  It
does NOT have algorithms to calculate Jewish holidays like Rosh
Hashanah, Yom Kippur, or Hanukkah.  I would like to amend this.
Can somebody take pity on a poor Gentile and tell me if there is
an algorithm that, given the year, will calculate the date of any
of the holidays?  If so, can someone send me the algorithm(s) or a
pointer to it/them?

I doubt that this topic is of great interest to the rest of this
newsgroup, and I don't read it regularly anyway (lack of time, not
lack of interest), so please reply via MAIL.  As a last resort if
you can't reach me by mail, post it to this newsgroup with "Calendar"
in the subject line; through the magic of "rn" I will monitor this
group for any such message.  Many thanks.
-- 
-- Greg Noel, NCR Torrey Pines       Greg@sdcsvax.UUCP or Greg@nosc.ARPA

rib@edsel.UUCP (RI Block) (10/02/84)

I hate to discourage honest enterprise, but an 'anaylitic'
conversion from solar (julian or gregorian civil) to lunar-Jewish
dates involves lots of calculations.

Jewish events fall at regular dates within the context of the
jewish calendar, e.g. Rosh Hashana is always 1 and 2 Tishri,
Pesach is always 15 Nisan.

The complication is that there are 6 different year lengths made up
of (leap [13 month] | common [12 month]) * (short|normal|long) years.
The choice of leap or common years is determined by the position in the
19-year cycle, the choice of lengths made by deleting/adding days to
two of the months. The nominal way to figure the calendar is to sychronize
the month with the lunation, but in practice, one of four delay rules
usually intervenes to guarantee, for example, that Yom Kipur never falls
on Friday or Sunday.

There are various citations in print and some netters have posted that
they have programs that do the conversion.

raphael@crystal.UUCP (10/09/84)

I have a program that converts solar-Jewish.  It is complex,
as previous articles have pointed out.  Mail me if you want a copy.

	Enjoy Sukkos.
	Raphael