Class: The Making of the Jewish Calendar

This coming Sunday evening, at 7 PM, we'll be looking at the Making of the Jewish Calendar, and specifically the question of what it was that Hillel II enacted in the year 359. The class is part History, part Calendar, and should be fascinating; preparing for this has made me a big fan of the work of Prof. Rachamim Sar-Shalom.

Here is a rough outline, as well as the source sheet I expect to distribute:

The Making of the Jewish Calendar

What were the original rules of the calendar?
Roots of the calendar - Creation through Egypt

The witness system
Witnesses
Interrogation
Mistaken courts
A response to Sadducees?

Who set the calendar?
Small groups
Secretive
Hoshana Rabbah announcement

What are the 5 rules of today’s calculated calendar?
Leap years
Length of years
Length of months
Molad
Rosh haShanah gets pushed off in four situations

When was calculation instituted?
Evidence
Cairo Genizah
Muhammad ibn Musa Al Khawarazmi (early 9th century)
Exilarch’s letter of 836

Hillel’s timeline and influences
325 - Council of Nicea
352 - Rava dies
359 - Hillel makes his enactment
Rav Hai Gaon’s testimony

But what, exactly, did Hillel institute?
A system with many rules, until 840
What Hillel has
Rosh haShanah can’t be Sunday - 7th century
3-6-8-11-14-17-19 is mid-8th century
Al Khawarazmi's 3-5-8-11-14-16-19, and how it may be matched to our 3-6-8-11-14-17-19 based on the three different "Year 1" counts
Full calculation of moladot

Evidence for Sar-Shalom’s theory
Al Khawarazmi’s 825 article is missing the initial molad point
Langerman's challenge, and Sar-Shalom's reply
The Exilarch’s letter
Rav Saadia Gaon vs Ben Meir

Sar-Shalom’s theory also explains the 642 chalakim in the battle of RSG and Ben Meir

Levinger’s challenge and Sar Shalom's reply

The lunation problem

Sources1. Bereishit 1:14
And Gd said: There will be luminaries in the heavenly sky, to distinguish between day and night and to serve for signs, appointed times, days and years.

2. Bereishit 7:11, 8:14
In the second month, on the 17th day of the month, on this day all of the springs of the great depths broke open, and the heavenly stores opened…
And in the second month, on the 27th day of the month, the ground dried.

3. Midrash, Pirkei d’R’ Eliezer, Chapter 7
On the 28th of Elul the sun and moon were created. The counts of years and months and days and nights and times and seasons and machzorot and intercalantions were before Gd, and He intercalated the year, and then passed these to Adam in the Garden of Eden, as it is written…

4. Talmud, Rosh haShanah 25a
The verse states three times (Vayyikra 23:2, 4, 37), “You shall call.” It is you - even in error. It is you - even intentionally. It is you - even if fooled.

5. Divrei haYamim I 12:33
And from the children of Yissachar were those who knew wisdom for the times, to know what Israel will do…

6. Talmud, Ketuvot 111a
Gd made them swear that they would not reveal the secret to idolaters.
Rashi: This is the secret of the ibbur or the secret of the explanations of Torah (or trop?).

7. Midrash, Shmot Rabbah 15:20
Intercalation of the year is done with ten elders… and so was done in the days of Solomon, when Solomon intercalated the calendar he brought in seven elders, as it is written…