On Monday, June 2nd, 2014, thousands of rabbis and laypeople will be learning in the Daf Yomi of the conflict between Rabban Gamliel and R’ Yehoshua. They probably won’t realize that hidden within their discussion is the key to the Sod Ha’ibur, the great secret of the Jewish calendar.

The Talmud, in Rosh Hashanah Daf 25, relates that Rabban Gamliel established Rosh Hashanah at sunset after the 29th day of Elul – a time when, from an objective perspective, the moon could not possibly have been seen. When R’ Yehoshua disputed his decision, calling for Elul to have 30 days, Rabban Gamliel humiliated him.

The widely held presumption is that R’ Yehoshua was correct in his belief that the witnesses should not be accepted. But to understand why Rabban Gamliel was forced to act as he did, we must investigate an event that occurred over two centuries later, in Hebrew year 4119 (358/9 CE), That year was considered by many to be the inauguration by Hillel II (Hillel ben R’ Yehuda) of the Fixed Hebrew Calendar, in use to this day.

This calendar is based on the Molad of Tishrei, the one Molad we do not announce on the Shabbat before Rosh Hodesh. It is thought that the Molad of the very first Fixed Calendar Rosh Hashanah was Saturday, 20 September 358 CE, at 5:12 PM, which is 23 hours and 233 halakim. This is at almost the end of the Hebrew day yet the Fixed Calendar system will push the start of Rosh Hashanah back almost 24 hours to just after sunset.

Those of you who have visited a planetarium have seen how astronomers can recreate ancient skies, so too can the skies that Hillel ben R’ Yehuda saw before dawn Erev Rosh Hashanah 4119 be recreated. Most surprisingly what Hillel II saw was a very bright Old Moon by the light of which it was possible to walk for almost an hour and a half. This was very much like the moon that plagued Rabban Gamliel centuries before.

Here is a link to this calendar data.

The inauguration party of the new Fixed Calendar is spoiled by a pesky old moon.

Furthermore, as Rabban Gamliel makes note in our Daf, “sometimes [the moon] travels a long route and sometimes [the moon] travels a short route.” We now have the science to understand that the moon of Tishrei 4119 took a long route indeed, starting with the conjunction somewhat below the Cape of Horn (Chile).

Here is a link to map showing the path of this moon.

Hence, we have a confluence of exceptional factors all of which resulted in the highly irregular occurrence of a visible Old Moon the morning of Erev Rosh Hashanah 4119. A study I have made shows that this confluence occurs for slightly less than 4% of all Moladot of Tishrei. Year 4119 was one of these, and this led to a misunderstanding on the part of Hillel II, and subsequently on the part of many traditional commentators down the ages.

Who was Hillel II? He is commonly referred to as Hillel the Patriarch. The myth that Hebrew Year 4119 marked the inauguration of the Fixed Hebrew calendar implies that Hillel II would have had to wield the authority of a Nasi in order to establish such a radical change in tradition. In fact, neither the Bavli nor the Yerushalmi, nor Saadya Gaon in his fight with Rabbi Meir, nor the 10th-century Iggeret Rav Sherira Gaon (a principal source of the history of the Talmudic period), nor the Rambam, make any mention of the establishment of the Fixed Hebrew Calendar in 358 CE nor of a Patriarch named Hillel.

We can however be certain that Hillel ben R’ Yehuda really did exist. The source document, a early 11th century responsum of R’ Hai Gaon cited by R’ Avraham ben Hiyya, gave us this auspicious date, 670 of the Seleucid era – Hebrew Year 4119. This could not have happened by a chance pick in a made up story. It had to be a real event.

Now back to the Daf we are learning on June 2nd of this year. We see there that the factor of significance is the visible Old Moon.

In fact It is a signature of the Fixed Hebrew Calendar that occasionally the Old Moon is seen in the morning before the Molad of Tishrei.

Combing through the study during the period of the lifetimes of Rabban Gamliel, we can find a likely time when the famous conflict with R’ Yehoshua actually occurred – in Tishrei 3881 (120 CE). The Molad for that year was Monday, at 21 hours and 601 halakim; again a late Molad, and again leading to a visible Old Moon on Erev Rosh Hashanah. Witnesses arrived declaring they had seen the Old Moon, causing trouble for Rabban Gamliel, who wished to announce Rosh Hashanah that same night. Everyone knew that you could not see both in the same period, and hence R’ Yohanan Ben Nuri exclaimed, “They are false witnesses!” and R’ Yehoshua followed suit.

Yet Rabban Gamliel was secretly using the fixed calendar, a calendar that mandates that Elul must be 29 days in length, a calendar that specifying the length of each lunar month. Essentially the same calendar we use to this day.

Rabban Gamliel had the Fix in – He was using our Fixed Calendar system.

All of this is something I explain in my book in much greater detail; but in any event, it helps us to understand the events in the Daf in an entirely different fashion: Rabban Gamliel was not being arrogant – he was following his Masoret and thus, very importantly, was providing the means by which Jews, far dispersed from Jerusalem, could know with confidence when to fast on Yom Kippur. The acknowledgement that the Nasi had the right to set the calendar was a cover for the fact that he was already using a fixed calendar. Only much later was the Fixed Hebrew Calendar made public. Rabban Gamliel preferred to retire with a cloud over his name than to reveal the secret entrusted to his family. This was then, the noble behavior we much prefer to encounter in Rabban Gamliel.

Those interested in these theories and other quite remarkable discoveries regarding the Hebrew calendar are welcome to contact me to receive updates regarding the imminent publication of my book Sod Ha’Ibur: Rethinking the Conflict Between Rabban Gamliel and R’ Yehoshua.