The Hebrew Calendar

The Hebrew Calendar

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For people who have embraced Torah observance later in life rather than having been born into it, the Hebrew calendar can be confusing, and even a point of contention. We want to observe the appointed times correctly, but the Torah does not provide calendar calculation specifics.

Established Israelite communities today (the various flavors of Judaism and the Samaritans) generally do not question the calendars they follow, as they have been in place for centuries. But are they correct?

Calendars in popular use today include the Hillel II1 (used by rabbinic Judaism), the Karaite method2 (new year declared when barley is ripened and months declared by observation of the waxing crescent moon) and the Samaritan calendar3 which is anchored for the most part to the vernal equinox for the start of year and the moon’s conjunction for months.

Several years into embracing and studying Torah, I was finally motivated to study the Hebrew calendar as the first step toward trying to get about a dozen people in our local Torah study group to be in sync by following a single calendar.

I was able to form an opinion on how the calendar should be calculated. This proposed calculation of the Hebrew calendar is very simple, but will not always line up perfectly with the methods commonly in use today. Neither the Jewish, Samaritan nor Karaite methods will always coincide with this calculation.

This proposed calculation is made up of two simple rules:

1. Each month begins the day after the moon’s conjunction (day as in the hebrew reckoning from sunset to sunset.)

2. The year begins with the first month after the vernal equinox.

That’s it!

The Samaritan calendar is closest of them all to this proposal, with the exception that they have fixed the date of the vernal equinox (which marks the beginning of Spring) to March 25th of the Gregorian calendar. I don’t know why they chose to do this. I suspect their calculation was created after the Julian calendar was implemented, when the vernal equinox did in fact land on March 25th. They may have ignored, or perhaps neglected to factor in, the drift in the vernal equinox over time earlier in March. This happens because the solar year is not exactly 365.25 days in length, meaning that even with the extra day of the leap year every four years, the actual solar year is still slightly at odds with our measurements.

Why so simple?

I suspect calendar calculation was originally very simple. I suspect the lunar and solar cycles were originally perfectly in sync, resulting in a solar year of 360 days containing 12 months (lunar cycles) of exactly 30 days, with the equinoxes and solstices perfectly aligned with new moons. Spring would have begun at the vernal equinox which would have also been synchronized with the conjunction of the moon. Four seasons of exactly 90 days each, marked by an equinox or solstice and synchronized new moon.

How simple would calendar calculation have been in this type of environment? So simple anyone could calculate any astronomical event with certainty well into the future. If there had been appointed times in year 1, simple multiplication would allow anyone to project the number of year/months/days between any current date and any future appointed time.

There would have been no reason to look for agricultural markers to determine when a season began. There would have been no waiting to see if a new year was going to begin or an intercalated month would need to be added. There would be no doubt whether the new month began this evening or the following. None of the difficulties which cause division today would have been present.

An original perfect 360 day solar year may not be provable, but calendars from many ancient societies have preserved the idea of a 360 day solar year made up of 12 months of exactly 30 days. The ancient story of the flood in Genesis reports exactly 150 days elapsing between the 17th day of the second month and the 17th day of the seventh month:

In the six hundredth year of Noah’s life, in the second month, on the seventeenth day of the month – on that day all the fountains of the great deep burst open and the floodgates of the heavens were opened. (Genesis 7:11 NET)

The waters prevailed over the earth for 150 days. (Genesis 7:24 NET)

The waters kept receding steadily from the earth, so that they had gone down by the end of the 150 days. On the seventeenth day of the seventh month, the ark came to rest on one of the mountains of Ararat. (Genesis 8:3-4 NET)

There also exist ancient claims that the solar year used to be 360 days:

References in the Vedic and classical Sanskrit texts explain why the length of a year and a month changed. These manuscripts point to a “cosmic upheaval in [the] remote past.” They explain that we used to have a 360-day year, but the Earth “underwent a total upheaval,” and as a result “the Earth’s period of revolution round the Sun in 360 days was changed to 365 days.” This also caused the Moon to undergo a “serious perturbation,” and “the period of lunation was very probably changed.” 4

The ancient Egyptians developed elaborate mythology to describe why the year was lengthened from 360 to 365 days.5

Today many have developed more scientific theories to describe how this happened, even claiming to rely on evidence seen in the exploration of space.6

If one accepts that the solar and lunar cycles used to be perfectly synchronized, it’s not terribly difficult to imagine that the cataclysmic events of the flood, or the events of the exodus, caused enough upheaval that the solar and lunar cycles ended up separated. A simple speed increase in the rotation of the earth on its axis would be enough to simultaneously shorten the day (and hence the month) and lengthen the year. The day would be slightly shorter, meaning more of them would elapse during the same solar revolution. Each month would be slightly shorter, and thus instead of 360 days of 12 months, 12 months is now approximately 354 days, while it takes approximately 365 days to complete a revolution around the sun. Both cycles are now similar distances from 360 in opposite directions.

Taking all of this into consideration, if we want to approach the simplicity of the original 360 day calendar, we should be consistent and match the original as closely as possible. Thus, if as Exodus 12:2 indicates, the year begins in the season we know today as Spring, then it should begin at or after the vernal equinox, rather than before. In my version of the ideal original calendar, the vernal equinox would have signaled both the Spring season and a new month. Nobody would have considered Spring to begin any sooner than this. Thus is should seem improper to allow the new year to begin before the vernal equinox, but it frequently does by the Jewish and Karaite methods of calendar determination (for example in this year, 2018). It should also not begin two new moons after the vernal equinox, which sometimes happens in the Samaritan calendar (in 2020 for example).

Using similar logic, the first day of the month would be the first day after the conjunction, not the day containing the conjunction. This way you don’t prematurely start the month before the conjunction, just like you would avoid starting the new year prematurely (before the equinox).

With this simple proposed calculation, any appointed time can be calculated well into the future based on modern astronomical calculations for the equinoxes and conjunction.

The Karaite method of observing the state of Barley in Israel is based on the following passages from the Torah:

(Now the flax and the barley were struck by the hail, for the barley had ripened and the flax was in bud. But the wheat and the spelt were not struck, for they are later crops.) (Exodus 9:31-32 NET)

The above passage describes the state of barley and wheat during the plague of hail. The barley was ripe, and wheat was not.

YHWH said to Moses and Aaron in the land of Egypt, “This month is to be your beginning of months; it will be your first month of the year. Tell the whole community of Israel, ‘In the tenth day of this month they each must take a lamb for themselves according to their families – a lamb for each household. (Exodus 12:1-3 NET)

Since we know the barley was ripe shortly before this point, we know the month of the exodus was soon after the barley was ripe.

Deuteronomy also says:

Observe the month Abib and keep the Passover to the LORD your God, for in that month he brought you out of Egypt by night. (Deuteronomy 16:1 NET)

Do the above passages require that we examine the state of barley in order to determine the beginning of the new year, or does they simply indicate that YHWH was instructing Moses and Aaron that the month they were in, on their existing calendar, was to be the beginning of the year?

After all, the Torah doesn’t explain how to calculate the calendar, only that the month they left Egypt was to be their first month of the year. This suggests they already had a calendar and knew how it worked. There is no reason to believe they didn’t. They likely followed the Egyptian lunar calendar of their day, or something similar to it.

The “month of Abib” may have been the name of the month they were in, or simply a way for YHWH to reference the month number they were currently in, rather than a commandment to observe the state of the barley, even though the Hebrew word abib indicates the ripeness of grain and is used in that context elsewhere in the Jewish Bible. After all, the season we call “Fall” here in the United States literally has to do with leaves falling7, but does it officially start with the autumnal equinox, or when enough leaves have actually fallen that we are comfortable declaring that Fall has arrived?

During creation, YHWH stated:

God said, “Let there be lights in the expanse of the sky to separate the day from the night, and let them be signs to indicate seasons and days and years (Genesis 1:14 NET)

Nothing about barley is suggested here, so in my opinion, there is no logical or scriptural reason that agricultural observation should play into the calculation of the calendar.

  1. Wikipedia, “Hillel II
  2. Nehemia’s Wall, “Aviv Barley in the Biblical Calendar
  3. Israelite Samaritans, “Calendar
  4. Did the Preflood Earth have a 30-Day Lunar Month?, Center for Scientific Creation
  5. Ancient Origins, “The Mythology of Nut, Mother of Gods
  6. Conservative News and Views, “Calendar: From 360 to 365
  7. Online Etymology Dictionary

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