Emuna: History of a Calendrical Dispute – and its Resolution

by Rav Shlomo Hecht, Beit Hillel rabbi, yeshiva.org.il, translated by Hillel Fendel.

The Jewish calendar marks the epitome of Jewish unity; the same one is used in every single Jewish community around the world. But for a few years over a millennium ago, it wasn't quite so uniform, and if the dispute hadn't been resolved, this year we would have had a problem…

This week's Torah portion of Bo features the commandment to fix an annual lunar calendar and sanctify each new month (new moon) as it begins. As such, now is an appropriate time to recall a major Rabbinic dispute of more than 1,100 years ago, which, most fortunately, was resolved "just in time."

The issue was: When certain specific events happen, how do they affect the determination as to which days of the week the festivals are to occur? This of course has major ramifications, and especially in a year like this one, in which according to one of the opinions, this coming Passover, which is set to fall out on Saturday night, would actually be on Sunday night.

On the one hand, R. Aharon ben Meir was the Rosh Yeshiva of Yeshivat Geon Yaakov in Eretz Yisrael, a direct descendant of Hillel the Elder and R. Yehuda HaNasi, and the leading scholar in the Land of Israel. On the other side stood a younger Torah scholar in Babylonia, a promising scholar named Saadia ben Yosef – soon to be R. Saadia Gaon.

Their dispute revolved around the question of a certain type of molad that comes out on Rosh HaShanah after midday. The molad is essentially the "birth" of the new moon, when it can first be seen after having disappeared from sight at the end of the previous month. The new month is generally declared a short time after the molad is, or could be, observed. However, one of the exceptions to this rule is that a molad zaken – a molad that occurs after midday on Rosh HaShanah – the holiday of Rosh HaShanah is pushed down one day, as are, consequently, all the succeeding festivals up to and including Sukkot. That is, if Rosh HaShanah was supposed to be on Monday, it would actually be on Tuesday instead – so as to ensure that the new moon is seen on the first day of the year and not afterwards.

Other considerations that must be taken into account when scheduling the year are 1) that Yom Kippur must not fall out on either Friday or Sunday, because of Shabbat considerations, and 2) that no year must be more than two days longer than another (not including the leap month of Adar Sheni).

The process of determining the calendar, briefly, depends on the determination as to whether the year is a leap year or not. Based on this, we calculate when the molad of the month of Tishrei will occur in the upcoming year and in the year following it. The theoretical date for Rosh Hashanah is established, and then the days of Rosh Hashanah for the two years are adjusted so that the length of the year does not require more than seven full months of 30 days or fewer than five.

The dispute between R. Aharon ben Meir and R. Saadiah in the fateful year concerned whether the slight gap between midday and the molad of Tishrei constituted enough of a delay. The molad was actually some 13 minutes after midday, and R. Aharon said that anything less than 35 minutes did not require pushing off Rosh HaShanah. The next year there was to be a similar discrepancy. According to the calculations, this dispute meant a gap of one to two days between when the holidays were to be scheduled for the coming years.

This year, 5785, similar circumstances apply, meaning that according to R. Aharon ben Meir, Rosh HaShanah next year should be on Monday, whereas according to our calendar, which follows R. Saadiah Gaon's approach, it is "pushed off" to Tuesday.

In addition to the High Holidays of 5786, the ramifications of such a dispute would also have determined how many days were supposed to be in the month of Cheshvan (it varies each year between 29 and 30), and when Pesach falls, etc. In 5789 and 5790, as well, there would be discrepancies between the two approaches, affecting, for instance, Passover of both 5788 and 5789 and the High Holidays and Sukkot of 5789 and 5790. However, once Cheshvan and Kislev come around and can be adjusted according to necessity, and given that most of the time the molad of Tishrei does not fall in the controversial time period, both approaches equal out by Chanukah, and peace and harmony are restored.

How did this dispute, which put the entire Jewish world of the time into a tizzy, begin? We do not have all the details, although much information was garnered when the Cairo Genizah was discovered. It was universally known that a molad zaken pushes off Rosh Hashanah – but R. Aharon ben Meir claimed that it was an Eretz Yisrael tradition that if the molad was less than 35 minutes after midday, Rosh HaShanah need not be pushed off.

R. Aharon further claimed, with Talmudic justification, that the Jewish world must follow the Land of Israel in these matters. What was Rav Saadiah's response to this claim? His principle response was that 600 years earlier, one of R. Aharon's predecessors and ancestors, Hillel the Elder, instituted the calendar, including the sanctification of all the months, from then on until the coming of the Messiah. As such, the Sages of Eretz Yisrael no longer have an advantage in determining the months and year.

Ultimately, the dispute was settled in that the Jewish world accepted Rav Saadiah's position, while R. Aharon's followers diminished in numbers.

Even though the dispute spread out over five years, under the same circumstances as these years, the dispute had already faded away by the last two years. Ever since then, the principles and rules for the Jewish calendar have remained uniform in all Jewish communities throughout the world, and we all follow the same exact calendar.

The unity of the Jewish People that is expressed, inter alia, in our uniform Jewish calendar is what brought about, with G-d's help, our ingathering from all corners of the world to the Land of Israel.

May G-d implant in our hearts, and in the hearts of all of Israel, love and brotherhood, peace and harmony.