Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 ggr 02/21/84; site edsel.UUCP Path: utzoo!watmath!clyde!burl!ulysses!mhuxj!ihnp4!edsel!rib 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 Lines: 19 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.