Molad Zakein · Rosh Hashanah comparison

Compare fixed-calendar Rosh Hashanah dates with the Ben Meir threshold of 18 hours and 642 chalakim. This study evaluates the Tishri molad and resulting postponements without changing leap-year placement or the mean-molad epoch.

Jewish Cosmology is an interactive research and educational web application connecting Hebrew dates, traditional Jewish calendar calculations and halachic concepts of time with the observable motions of the Sun, Moon and planets, astronomical seasons and eclipses.

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