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From: rhendel@mcs.drexel.edu (Russell Hendel) Date: Thu, 3 Oct 1996 19:57:41 -0400 Subject: Birchat Chama vs Harath Olam; 2 sources for Jewish Calendar Rick Turkel [V25n6] inquires why HARATH OLAM refers to Tishray as the creation of the world but nevertheless Bircath Chama revolves around the sun returning to its original position in Nissan. The simple answer is that the Jewish calendar has two conflicting sources. Very roughly, the lunar months and years start in Tishray when the world was created while leap years are depedent on when Spring and Pessach fall out which according to Ex 12,1 is connected with Nissan. A complete account may be found in Rambam, Calendar laws, 6-10. Some details are as follows THE LUNAR PROBLEM: The lunar month is about 29.5 days; but we cant start a month in the middle of the day (6:5, and 8:1). The SOLUTION is to make full and empty months (e.g. 8:6)--some being 29 and some 30. This requires calculating when the lunar conjunction occurs and these CALCULATIONS start from the first lunar month in the first Tishray(6:15,10:3). THE SOLAR PROBLEM: Just as a month cannot start in the middle of a day so too the solar year---when the earth returns to its original position--cannot take place in the middle of a month(9:1). The SOLUTION to this problem is to make leap and non leap years(6:10). This requires calculating the position of the sun against the background of stars and this calculation always starts from its position in Nisan(10:3). The reason for this is because the court had to decide when to make a year a leap year to e.g. let Pesach coincide with the spring (10:6). The SOLAR CYCLE--the time required for the sun to return to its original position is 28 years. The LUNAR_SOLAR cycle--the time required for a pattern of leap and non leap years with full and deficient months to return to its starting point (with a 1-2 hour error) is 19 years. I hope this clarifies the matter. Incidentally, similar problems and resolutions exist in most other cultures. Russell Hendel, Ph.d., ASA, rhendel @ mcs drexel edu