Sefer Ivronoth

Contains intricate formulae and calculations to determine the New Moons, Solar and Lunar cycles, Seasons and systems of intercalculation. The author cites a calendral chant composed by the renowned Gaon Rabbi Israel Auerbach of Mehzritch who explained the formulae to the author (f.10). The author also cites other published Ivronoth texts and relates how his methods differ and improve upon theirs (f.11r, 28). He further cites his own original calculations “Devar Chochmah Asher Lo Haya Le’olamim” (f.6v) and concludes by stating: “Understand this well...for it is great and wonderous...which the early scholars did not think of and left a place for me...” (f.7r). The final section contains comparative charts to various Christian calendars noting the important holidays and fairs and indicating how various holidays are observed on a variation of dates depending on the country. The final leaf (f. 51) contains predictions for years of hunger or abundance dependent on particular weather conditions during particular months.