A 35-minute calendar dispute nearly split the Jewish world, until Saadia Gaon intervened
In 922 a rabbi in Palestine claimed the Jewish calendar's noon cutoff for dating new years was really about 35 minutes later. It sounded trivial, but it would have put Passover on different days in Palestine and Babylonia. An Egyptian-born scholar named Saadia wrote the rebuttal that held the calendar together.
Saadia ben Yosef was born in the Fayyum of Middle Egypt in 892, which is why Arabic sources call him al-Fayyumi. At 20 he began a Hebrew dictionary, the Agron, and at 23 wrote an attack on the Karaites, Jews who rejected rabbinic tradition, a fight he pursued all his life. That same year he moved to the Land of Israel to study in Tiberias, and in 926 he settled in Babylonia, the great centre of Jewish learning in the Abbasid Caliphate.
The calendar fight made his name. Since the time of Hillel II, the Jewish calendar had run on fixed rules rather than sightings of the moon, including one that postponed Rosh Hashanah when the calculated conjunction fell at noon or later. Aaron ben Meïr, head of the Palestinian academy, claimed the true cutoff was 642/1080 of an hour past noon. In that year it would have meant a two-day gap: Passover on Sunday by his reckoning, Tuesday by everyone else's. Saadia's Book of Festivals refuted him and averted a schism.
In 928 the Exilarch David ben Zakkai made him gaon, head, of the ancient Sura academy, though no foreigner had held the post and his family lacked prestige. An elder warned the two strong personalities would clash, and they did. When Saadia refused to sign a ruling he considered unjust, each man excommunicated and tried to depose the other, and Babylonian Jewry split for years before a reconciliation.
His lasting legacy is intellectual. Saadia was the first major rabbinic author to write extensively in Judeo-Arabic, and his Book of Beliefs and Opinions was the first systematic attempt to fuse Jewish theology with Greek philosophy. His Arabic translation of the Torah, the Tafsir, was copied into nearly every Yemenite manuscript, though critics such as Abraham ibn Ezra mocked some identifications; he rendered the biblical re'em as rhinoceros. He died in 942.
Source: Saadia Gaon
