Tale of Two Geonim: The Calendar Controversy That Shaped History

We've all heard about the era of the Geonim and the famous scholars who led the Jewish people, like Rav Hai Gaon and Rav Saadia Gaon. The Geonim were based in Babylon, of course, but not many know that even in the Land of Israel, throughout the era of the Geonim and beyond, there was a 'Gaon' at the head of the 'Yeshiva of the Land of Israel'. Communities would direct questions to him, much like they did with the Geonim of Babylon. In one notable instance, a significant disagreement arose between the Geon of Israel and the Geon of Babylon.

We're talking about the period when the Land of Israel was under Muslim rule. Very little documentation from this time exists, so for generations, not much was known about the Yeshiva of the Land of Israel and its Geonim. Only with the discovery of the Cairo Genizah, were we able to shed light on the history of the Yeshiva of the Land of Israel and its Geonim.

The last known response from the Geonim of Israel is from the year 960, addressing the 'Men of Rhineland', the Jews of Ashkenaz from the ShUM communities — Speyer, Worms, and Mainz, located on the Rhine. This year marks the birth of Rabbeinu Gershom Me'or HaGolah. Yet, a hundred years later, we still find mentions of the Yeshiva of the Land of Israel in Ashkenazi prayers. This refers to a famous prayer still recited today, the prayer of Yikum Purkan, appearing in the Machzor Vitry from Rashi's students, stating: 'To our masters and rabbis, the holy congregation in the Land of Israel'.

It's interesting to note that even though the yeshiva was originally in Tiberias, after the destruction of Tiberias, the remaining sages moved to Jerusalem and established their yeshiva there. However, the head of the yeshiva continued to be called the 'Gaon of Tiberias', reflecting its founding and long-standing presence (similar to today's Hevron Yeshiva named after its original establishment in the city of Chevron, even though it moved to Jerusalem after the 1929 riots).

The authority for intercalating the years and determining the calendar was always held by the Great Court in Israel. However, with Roman persecution banning activities like declaring the month, witnesses, etc., Hillel the Second, the last president descending from Hillel the Elder, established a permanent calendar, allowing the calculation of years and months until the arrival of the rightful redeemer. Nonetheless, each year, the Geon of Israel would declare the order of the upcoming year and send it to Jewish communities everywhere.

In the year 922, a seminal event occurred in Jewish history: the Geon of Israel sent a calendar to all Jewish communities, and the Geon of Babylon challenged it publicly: The calendar was flawed, and Rosh Hashanah and Passover should be celebrated on Tuesday, not Sunday, as the Israeli Geon declared!

The head of the yeshiva in Israel was Rabbi Aharon ben Meir, supported by the communities in Israel and neighboring Egypt, while Rav Saadia Gaon, head of the Babylonian exile, opposed him. For two years, holidays had separate dates in Israel and Babylon.

Rabbi Aharon ben Meir sent a detailed letter to the Babylonian scholars, stating 'the instructions we received from Rabban Gamliel our ancestor... as taught and inherited from our ancestors, Rabban Gamliel the president and Rabbi Judah the president...'. Rav Saadia Gaon replied with a harsh letter, asserting that Rabbi Aharon ben Meir misunderstood the traditional teaching of the presidents and made an incorrect determination. This fierce dispute continued, as noted, for two years, and concluded in the year 924, precisely eleven hundred years ago, when the law was confirmed according to Rav Saadia Gaon. We continue to use this calculation to this day.