For centuries, the preponderance of thought has been that the Fixed Hebrew Calendar we use today was established in 358 CE by a Patriarch named Hillel II. In recent times there have been claims that the calendar may have evolved many centuries later.

But a simple mathematical relationship which I will now describe and clay tablets found in the sands of Iraq should change our collective mindset and cause a rethinking of what we know about the Hebrew Calendar. The Fixed Hebrew Calendar was actually established in 791 BCE.

It has escaped notice that the Hebrew Calendar contains the seeds of it’s origin. Every month we add 29 days 12 hours and 793 halakim to the previous month’s Molad, and announce the result on Shabbat Mevorchim in synagogue. As we go back in time, month before month, should we not eventually arrive at the point at which the calendar’s originators began it — namely, zero hours and zero halakim?

I am not referring to what is known as the Molad of Tohu, the New Moon of Creation. That was set at September 6, 3761 BCE 23:11, but is not actually a zero hours zero halakim point. The zero hours zero halakim point would fall when the calendar’s originators lived, as they would begin to calculate from that time.

I built a table of all of the Moladot, starting with the Molad of Tohu, and extending all the way to the Molad of Tishrei 2020 — a total of 71,943 entries, an enormously lengthy table.

Then I searched for the zero hour — zero halakim points. Only three times since the Molad of Tohu did the Molad fall at zero hours and zero halakim.


2887 BCE, was much too early, 1306 CE was much too late, but (drumroll, please!) 791 BCE was just right — since it was around this date that it was becoming known in Babylonia (and thus in Israel too) that the average length of a Synodic Month was 29;31:50:08:20 days sexagesimal and 235 lunar months are practically equivalent to 19 solar years.

Presto! These are the key parameters of the Fixed Hebrew Calendar.The average Synodic month length is the same as 29 days 12 hours and 793 halakim. GUcHADZaT is the mnemonic for the years to which we add the leap month of Adar Rishon.

Parker and Dubberstein, analyzing clay tablets found in the sands of Iraq, determined in Babylonian Chronology, 626 B.C. — A.D. 45, that during the period of 490 BCE through 312 BCE the Babylonians began to distribute their 7 thirteen month long years according to the series 3-6-8-11-14-17-19. That is the series we call GUCHADZaT!

It was thought to be an arbitrary choice of the Babylonians to use this series, but now we can see our forced residency with them as the likely cause. They were sharing technology we had developed 300 years before.

This gives us a double confirmation that the Fixed Hebrew Calendar dates back to these times.

But wait, there’s more! Taking the traditional historical view of the rabbis, King Solomon died in 796 BCE, and subsequently, in the reality of a divided kingdom, Jeroboam ben Navat led the kingdom of Israel in the North. I suggest that to disassociate his subjects from the Kingdom of Judah, soon after his rise to power (say in 791 BCE!), he disconnected from witnessed-based calendar and adopted the very same Fixed Hebrew Calendar we use to this day.

Why, you ask?

Well, the premise for my book was my discovery of a strange anomaly, that the Molad of Tishrei according to the calculated calendar that we use, always falls at least one day earlier than the actually New Moon, often two days and sometimes even three days. For example, Rosh HaShanah 5775 is now upon us. The calculated Molad of Tishrei will be Wednesday, 14 hours, 339 halakim. Even with Lo ADU Rosh, a rabbinical dehiyyah deferring Rosh HaShanah 5775 to Thursday, the Molad still falls one day before the New Moon, which will not be visible until Thursday after sunset i.e. Friday.

This fact first began to puzzle me back in 2002, until I delved into lunar science and traditional sources, and began to grasp that it might have been done deliberately. I first gave one possible explanation for this in my book, but recently added the one I’ve just outlined above – a political motive, to set the two kingdoms of Judah and Israel apart, inasmuch as they would now keep different times and festivals!

I have been asked if we should return to an actual witnessed based calendar. Why would we want to? The one we have has only worked for 2804 years.

May Rosh HaShanah 5775 usher in a new period of Peace for Israel and all the World. Shana Tovah.

To learn much more about the Hebrew Calendar and to dispel some of the myths surrounding it, you can buy my book, Sod Ha’ibur — Origin of the Hebrew Calendar — Conflict between Rabban Gamliel and Rabbi Yehoshua. In Israel it is available in the Moriah bookstore in Jerusalem’s Old City, (02) 628-5267, while in the USA or Europe you can buy it at this link.