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From: Russell Hendel <rhendel@mcs.drexel.edu>
Date: Tue, 10 Aug 1999 01:17:53 -0400 (EDT)
Subject: Does the molad ever occur after Rosh Chodesh?

Jonathan Grodzinski raises the issue of the principles by which the
Jewish calendar is calculated (V29n33). A few points of clarification
are in order

1) ALL LUNAR MONTHS ARE CALCULATED: There are 5 principles:
---First Molad of Tishray, Year 0, was at Day 2, 5 hours, 204/1080
---Every 19 year cycle add 2 days, 16 hours, 595/1080
---Every leap year adds 4 days, 8 hours, 876/1080
---Every non leap year adds 5 days, 21 hours, 589/1080
---Every month adds 29 days, 12 hours, 793/1080.

So if I wanted the molad of Marcheshvan of the year 5700 = 19*300
I would
----------take 2 days   5 hours 204/1080
----------add 300 x( 2 days, 16 hours, 595/1080)
----------add 29 days, 12 hours, 793/1080.

(Source: Chapter 6, Rambam, Laws of Lunar Months) It is possible to make
a simple excel workbook exhibiting all 72000 months

2) The ANNOUNCED DAY OF THE MOLAD may differ from the Calculated day
according to 4 exceptions presented in Chapter 7(For example Rosh
Hashana can never occur on Sunday Wednesday or Friday).

The Rambam EXPLICITLY gives the reason for the laws in Chapter 7 as
because all calculations are averages(paragraph 7)

Over the past few years several people have offered programs doing this
I am simply adding the point that it can be done in spreadsheet form for
all known months of Jewish history

Russell Hendel;Phd ASA;Moderator Rashi Is Simple;http://www.shamash.org/rashi