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From: rib@edsel.UUCP (RI Block)
Newsgroups: net.religion.jewish
Subject: Re: Algorithm for Calendar Date of Jewish Holidays?
Message-ID: <272@edsel.UUCP>
Date: Tue, 2-Oct-84 14:03:24 EDT
Article-I.D.: edsel.272
Posted: Tue Oct  2 14:03:24 1984
Date-Received: Wed, 3-Oct-84 20:03:39 EDT
References: <139@sdcsvax.UUCP>
Organization: AT&T Bell Laboratories, Piscataway
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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.