JEWISH MOMENTS IN THE LAND OF ISRAEL
921.
The Great Hebrew Calendar Controversy:
When Jews Celebrated the Holidays on Different Days

In 921–922, a technical dispute over the Hebrew calendar became a struggle over who held religious authority in the Jewish world. Palestinian sages in Jerusalem, led by Aaron ben Meir, challenged the long‑standing Babylonian system that fixed festival dates for communities across the Diaspora. Saadia Gaon’s intervention defended the established calculations and preserved communal unity. Beneath the astronomy lay a deeper issue: whether Jewish sacred time and covenantal life would be anchored institutionally in Babylonia or symbolically in the Land of Israel.

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In 921–922, a major controversy erupted in the Jewish world about the precise details of the Hebrew calendar for the coming years. For almost five centuries, the calendar had been determined by fixed mathematical rules traditionally associated with Hillel II in the mid-fourth century, replacing the earlier system based on direct observation of the new moon in the land of Israel. This shift from eyewitness testimony in Jerusalem to a rule-based calendar meant that, even in exile, Jews everywhere could observe the festivals on the same dates. Yet, the authority to define those dates still symbolically rested with the ancient institutions of the land of Israel.

In 921, on Sukkot, from the Mount of Olives overlooking Jerusalem, the leaders of the Palestinian community, headed by Rabbi Aaron ben Meir, publicly announced the calendar for the next three years according to their own........

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