Question: I am interested in whether the Day of Atonement (10th of Tishri) was calculated in 30 A.D. by the phase of the moon, or by the Barley harvest -- did the Barley harvest have anything to do with the Jewish Calendar? Could you please advise me as to whether the Day of Atonement in 1844 (September 23, according to the Jewish Almanac) was figured according to the phase of the moon, and did it take into account the time of the Barley harvest? All things considered, has the Day of Atonement (10th of Tishri) ever occurred so late as October 22?
Reply: During 2nd Temple times and for about 300 years more, the calendar was based on observation of the new moons, the harvests and the birth of lambs. When necessary extra ("intercalary") months were inserted into the calendar in the Spring or the Fall. For the spring season, the essential harvest was barley, and enough lambs were necessary for the Passover. For the early summer Feast of Weeks (=Pentecost), the wheat harvest was critical. Since the essential harvest for the Day of Atonement season was the Grape/Olive harvest it is very unlikely that the Day of Atonement was ever as late as Oct. 22nd.
When Christians came to dominate the Roman Empire, they tried to disrupt the Jewish religion by preventing the Jews in Jerusalem from communicating with the many Jews outside Israel (the Diaspora) on calendar details. This forced the Jews to switch to a computed calendar, which they have used without change since at least 1000 A.D. In 1844, they would have used the computed date of the Day of Atonement. You may find some details of the computation at

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