What Happened with the Calendar in September 2022

What Happened with the Calendar in September 2022

Yoel Halevi 2 comments

Many people are asking themselves why there is a difference between the sighted new moon and the rabbinic calendar. Some have offered several explanations, but in truth I find most of these explanations unfounded and not historical.

The following is an extremely short description which does not do justice to this very long and complicated subject. 

First it must be established that the rabbinic calendar in its original setting was designed to indicate when the new sliver would be visible. This was the basis of the calculation from its birth and it is clearly stated so in Mishnaic and Talmudic sources such as Rosh Hashanah 20: a-b. With the demise of the Jewish community in the land of Israel during the Byzantine era the power of the calendar when into the hands of the Babylonian diaspora which had received permission from Hillel II to use the calculation abroad. During the intermediate period (from around the 4th century to the 10th) the calendar calculation was confirmed by sighting the moon in the land. The diaspora relied on the calculation but did not have the means to know when the moon was sighted. This led to a discrepancy in the calendar the moment the diaspora no longer knew when the moon was sighted.

What is actually described in the Bible

In truth the bible does no lend any information on the exact way the calendar is to be used. We assume that the terms ḥodeš and yeraḥ mean the new sliver. However, this is only an assumption which cannot be proven unless we look to the other cultures around Israel at the time. The northern cultures such as Phoenicia, Emar and Babylon used the new sliver while Egypt used the waning moon. It also must be stated that we do not know from Exodus 12:2 which method is being referenced- waning, conjunction or waxing.  To make things even more complicated, Genesis 8:3 uses a 360-day calendar which means all month were 30 days long which is not how a lunar cycle works. We also find a strange statement in 1Sam 20:5 where Jonathan states that “Tomorrow is a new moon”. We do not know when they met but the fact that they go out the field may indicate a need for privacy which cannot be attained in the place during the day. This may lend to the possibility that they were looking and the waning moon. This is a matter of interpretation, but it is possible. 

The only time we know when people were using an exact system comes from the second temple era. 

Stage 1- 2nd temple to the 4th century

As it seems, the earliest we know for sure that the sighted sliver was the indicator of the new month goes only into the second temple. During the first temple era we only can assume it was the same. However, calendar disputes during the 2ndtemple lend to questioning if this was always the case. Jubilees uses a 364-day calendar which uses only a solar cycle (Jubilees 6:36-37). Ben Sira objected to this method and presented a completely lunar calendar (Ben Sira, 43:6-8). The 4Q317 scroll is an ongoing argument between at least three scribes who disagreed over the way to calculate the 364-day calendar. The Qumran community held a different calendar that the Pharisees and even the Sadducees which used a 364-day method (4Q332, 4Q333, 4Q169, 5Q11). 

The short of this is that we don’t know for sure. The only reason we use the new sliver is because that is the information we received from the Pharisees and later on by the sages (Philo mentions a lunar-Solar calendar, The Laws in Detail II, 41:140-142). In the tractate of Rosh Hashanah, we are given a description signal fire used to let the diaspora know the moon was sighted. After some time, messengers were sent to the diaspora due to an issue with false fires being used by groups who disagreed with the Pharisees. 

After the destruction of the 2nd temple the center of power moved to low land of Judea and later on the north. During this era, it was in the power of the local rabbis to decide when the new moon was sighted and declare the new month. This method was based on an elaborate calculation which was being perfected all the time. However, no matter what the calculation gave, only the sighted new moon was the final evidence used.

Stage 2- 4th century to 9th

During this period the calculation was taking place in the land. Rabbis outside of the land were given permission to use the calculation due to the Romans preventing information to flow from the land to the diaspora. 

However, by this point many other factors came into play in the calculation. Different rules of postponement were introduced. The first rule states that the sixth moth is never 30 days (Babylonian Talmud, Rosh Hashanah 19: b). 

Then new math rules applied to astronomical calculations dictated that to keep the years balanced in the solar cycle some adjustments had to be made. This led to a rule that we should not have the first day of the seventh month on Sunday, Wednesday and Friday. The reason behind exactly why these days is a problem is obscure, but it has been suggested it has to do with having a dead person be left unburied or the loss of field work. In overall it seems that the rule was used only when something serious might happen. 

Together with these base rules another rule came into play which had to do with the time of the conjunction. If a conjunction happened after mid-day the moon was expected to appear only on the next day. However, of the conjunction would be early in the morning or at night the moon should appear on the same day. This rule became the center of dispute between Ben Meir in the land and Rav Se’adya in Babylon around the year 921/2. Without going into the fine details of this dispute, which we have the letters which were sent between the two rabbis, this dispute is one of the reasons the calendar is sometimes off.  

There is a dispute when exactly the calendar was finalized. Some date it to the 9th century while others to around the 10thand even later. No matter when exactly this happened, it seems to be that after the center in the land was completely destroyed during the crusades, the center of power moved to Babylon where they developed and followed a different method than the one which originated in the land of Israel. This method no longer cared if the new moon was sighted and focused on when the conjunction happened. If the new moon was seen on the same day as the calculation, it was of no meaning to this method. In time the Babylonian Talmud and its methods took over the Jewish world, and with it the calendar and the power of local surviving practices in the land of Israel were dead.

What happened in September 26th-27th 2022?

On September 27th 2022 the conjunction accrued during the morning well before mid-day. When this happens, the assumption is that the new sliver will be visible in the evening. Taking into account that the sixth month is never 30 days in the rabbinic calendar, the beginning of the seventh month stared a day before the theoretical new sliver. This is why the rabbinic rule is to keep two days of Rosh Hashanah. In reality, the conjunction happened to late for the moon to be visible on the evening of September 26th making the visible day only one day later. This is a result a faulty calculation based on the Babylonian method which wants the conjunction to happen on the first day and not the sighting. However, the rule in the Talmud clearly states that the moon needs to be sighted. 

Today there are people who are very aware that the calculation used has issues, and in a paper from 2009 by a mathematician it was suggested to realign the calendar so it will fit the actual sighted moon. Rabbinic Jews who are in the field of the calendar are very aware that there is an issue, but the power of at least 800 years of practice is very difficult to change. 

For further reading on this topic:

Ben Dov, Jonathan (Editor), Wayne Horowitz (Editor), John M Steele (Editor), Living the Lunar Calendar, Oxford, 2012.

Cohen, Mark, Festival and Calendars of the Ancient Near East, Bethesda, Maryland: CDL Press, 2015.

Stern, Sacha, Calendar and Community: a history of the Jewish Calendar 2nd cent. BCE-10th cent. CEOxford, 2001.

  • The Jewish Calendar Controversy of 921/2 CE, Brill, 2019.

מרצבך עלי, רביב ערן, הלוח העברי הקבוע תולדות ומבנה, ירושלים, 2021. 


Ana Lopes

October 9, 2022 at 7:29 pm

Very interesting and very informative!
Thank you, Yoel!

Marc Thompson

October 13, 2022 at 5:32 pm

This is enlightening! Please don’t be offended if I ask a question about the final two days of Yeshua of Nazareth’s life… so I ask forgiveness now? Is there any way whatsoever to know the exact day of Yeshua’s “last supper meal” and the day and time of His crucifixion? In my mind it is not possible to have Him executed on Friday afternoon and risen “before” sunup on Sunday… and get 3 days from that! Is there any way to know what calendar was being used in the Temple observance on that specific day, or month in the years between 29-33 CE? In my mind as a follower of Yeshua… He would’ve known the truly biblical/Tanakh calendar as established by Yehovah. It would appear to me He would’ve had the last supper between the evenings on the 3rd/4th day (Tuesday/Wednesday) or the 4th/5th day (Wednesday/Thursday). If this is the case… the last supper wouldn’t have been a Passover seder observance in alignment with the Pharisee/Sadducee calendar!! Thank you for your time and if you choose to dismiss this comment or questions… I fully respect your decision. My only defense is that I, like many others am simply seeking truth… and not accepting the traditions of men! Shalom to you…

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