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The Jewish Year

The Jewish Year

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The Jewish year starts on Rosh Hashanah, "the Head of the Year," the day when Adam and Eve were created. The number of any given year (at the time of the writing of this article, the year is 5767 (2007)), is the amount of years which have elapsed since creation.

To find the corresponding Jewish year for any year on the Gregorian calendar, add 3760 to the Gregorian number, if it is before Rosh Hashanah. After Rosh Hashanah, add 3761.

Length

A standard Jewish year has twelve months; six twenty-nine-day months, and six thirty-day months, for a total of 354 days. This is because our months follow the lunar orbit, which is approximately 29.5 days. Due to variations in the Jewish calendar,1 however, the year could also be 353 or 355 days.2

Leap Years

The Torah says, "Guard the month of the spring, and make [then] the Passover offering."3 Meaning, we need to ensure that Passover is celebrated in the spring.

In fact, all the biblical festivals -- Passover, Shavuot and Sukkot -- are dependant on the agriculteral seasons. Shavuot is "Chag HaBikurim" (the First Fruits Festival) and Sukkot is "Chag Ha'Asif" (the Harvest Festival). We need to make sure that all the festivals are celebrated in their proper seasons.

Thus the Jewish lunar calendar must coordinate with the cycle of the sun and the seasons which are determined by the solar orbit. The problem is that a lunar year, twelve lunar months added together, only adds up to about 354.4 days.4 A solar year, at almost 365.25 days,5 is nearly eleven days longer. If no adjustment is made, Passover would occur eleven days earlier each year, eventually drifting into winter, then fall, summer, and then spring again.

The solution is to periodically insert an extra (thirty-day) month into a year, creating a thirteen-month year. Such a year is called a shanah meuberet ("pregnant year") in Hebrew; in English we call it a leap year, and it makes up all the lunar calendar's lost days. It happens about once every three years.

The month is added to Adar, the last of the twelve months. On leap years we observe two Adars -- Adar I and Adar II.

Thus, the Jewish calendar is both lunar and solar; the months are lunar months while the years are solar years. This is in contrast to the Gregorian calendar, in which the year is a solar year and the months are formed by dividing a year into twelve parts, and is also quite different from the pure lunar calendar observed by certain religions, in which each month is determined by the moon and a year is simply twelve lunar months strung together.

Hillel's Fix

While the Sanhedrin (Rabbinical Supreme Court) presided in Jerusalem, there was no set calendar. They would evaluate every year to determine whether it should be declared a leap year.

When Hillel II instituted the perpetual calendar in anticipation of the disbandment of the Sanhedrin (see Months), he also incorporated leap years into the calendar.

Hillel's calendar runs in nineteen-year cycles, each cycle containing seven leap years: the 3rd, 6th, 8th, 11th, 14th, 17th, and the 19th years.

The length of the standard leap year is 384 days, though it could also be 383 or 385.

There are exactly fourteen different patterns that the Hebrew calendar years may take, distinguished by the length of the year and the day of the week on which Rosh Hashanah falls. Because the rules are complex, a pattern can repeat itself several times in the course of a few years, and then not recur again for a long time. But the Jewish calendar is known to be extremely accurate. It does not "lose" or "gain" time as some other calendars do.

Before the Fix

Sanhedrin considered several factors in the course of their deliberations whether to declare a leap year on a given year. The primary factor, which overrode all others, was the spring equinox. If the spring equinox would fall later than the first half of Nissan (i.e., on the 16th or later), then the year was automatically declared a leap year. This is because, as mentioned earlier, the verse states: "Guard the month of spring, and make [then] the Passover offering."6

However, it wasn't enough for Passover to fall after the equinox, when it was "officially" spring; spring-like conditions needed to be evidenced. If in the land of Israel, the barley had not yet ripened,7 and the trees were not yet blossoming with seasonal fruit -- that, too, was sufficient reason to delay Nissan by adding a second month of Adar. Spring had to be felt; it had to be bright and green.

There were also several non-season-related factors which the Sanhedrin considered. For example, if the roads or bridges were in disrepair due to the winter rainy season, impeding the ability of the pilgrims to travel to Jerusalem for Passover.

For a mystical understanding of the solar-lunar calendar we follow, see The Nineteen-Year Marriage.

FOOTNOTES
1.

Two months on the Jewish calendar -- Cheshvan and Kislev -- can be both thirty days, both twenty-nine days, or one of each.

2.

This after Hillel established the perpetual calendar -- see below for more on this subject. Beforehand, the length of the years depended on the amount of thirty and twenty-nine day months, which depended on the monthly deliberations of the Sanhedrin (see Months).

3.

Deuteronomy 16:1.

4.

354.372 days, to be exact.

5.

365.242199 days, to be exact.

6.

This only means that Passover must fall out during the spring; the first of the month may actually be before the equinox as long as Passover (the fifteenth of the month) is on or after the equinox.

7.

The barley was needed for the omer sacrifice which was offered on the second day of Passover.

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Discussion (10)
April 18, 2013
Mina Kuttner's question about 1080 parts
The simple answer is that this derives from an old Babylonian system of measurement of time. The day was divided into 360 degrees and each degree into small units, 72 to a degree. If the day is divided into 24 hours, each barleycorn would be one-1080th of an hour.
Seth Ward
Denver
January 1, 2013
year 5773 out 6000 and more
How come when study when the creation till Nehemia and 69 weeks of Daniel 9, I counted 4000 years and if I had our common era years I arrived at 6000 and more years?
Patrick
Canada
November 26, 2011
how yrs we are talking here.
Daniel 12:7 It will be for an appointed time,appointed times and a half.
so how you calculate this?
Ruth
Tobyhanna, PA/USA
August 17, 2011
Re: Accuracy of Jewish Calendar
You are indeed correct that it is slightly off. The truth is that Maimonides himself writes in his Hilchot Kidush HaChodesh that the calculations he gives are not exact, but that they are good enough for our purposes.

This discrepancy has been discussed in a number of recent publications that deal with the Jewish calendar. Some have pointed out that any real halachik issues with regards to the calendar as it pertains to when Passover falls out, will happen only after the year 6000.

The Talmud tells us that this world, as we know it, will last for six thousand years, with the seventh millennium ushering in the cosmic Shabbat, the Messianic Era. For more on this see What is the significance of the year 6000 in the Jewish calendar?
Yehuda Shurpin for Chabad.org
August 16, 2011
Reference for Jewish Calendar reform
My suggestions to improve the Jewish Calendar originate in the book "Rabbinical Mathematics and Astronomy", by W. M. Feldman; Third, Corrected Edition; 1978, Sepher-Hermon Press, 53 Park Place, New York, N. Y., 10007.
Bert Katz
Silver Spring, MD
August 15, 2011
Proposed correction to the Jewish Calendar
The accumulation of error in the Jewish Calendar can be halted by replacing a 19-year cycle (with 7 leap years) with an 11-year cycle (with 4 leap years) once out of every 18 of the 19-year cycles.

The shortest repeated cycle would then be 334 (= 17 X 19 + 11) years. This results in one less leap year (i.e., 30 fewer days) every 6346 (= 334 X 19) years.

If Moshiach has not come by then, the target years for the first 11-year cycle could be 6062 - 6072. This year 6062 represents the year following the end of the 19-year cycle when Hillel II promulgated the current Jewish Calendar, plus six of the 17 cycles of 19-years = 4124 + (6 X 17 X 19).

If 334-year cycles are observed starting at that point (6073), the error accumulated since the year 4119 would stop growing. The insertion of five more 11-year cycles in years 6073-6127, followed by observance of the 334-year cycle, would additionally eliminate the accumulated error, allowing Passover to fall as early as the Vernal Equinox.
Bert Katz
Silver Spring, MD
August 14, 2011
Accuracy of Jewish Calendar
"But the Jewish calendar is known to be extremely accurate. It does not "lose" or "gain" time as some other calendars do."

I wish this were so. Unfortunately, the Jewish year of 365 days, 5 hr., 55 min., 25 25/57 sec. is too long by about 6 min. 40 sec. relative to the Solar Year, which is 365 days, 5 hr., 48 min., 46 sec. This results in an error of about 1 day every 216 years. This error has been accumulating ever since Hillel II promulgated his marvelous system. It is a smaller error than the Julian Calendar which was the secular calendar used in Hillel II's time, but the Gregorian Calendar is more accurate.

Currently, Passover falls more than 30 days after the Vernal Equinox 4 times in every 19 years. The number of late Passovers will continue to increase until the Moshiach comes, or when some improvement to Hillel II's marvelous system is allowed.
Bert Katz
Silver Spring, MD
September 30, 2009
RE: The article:
Thanks for pointing that out. This fact is codified by Maimonides in Hilchot Kidush HaChodesh 6:2.
Menachem Posner for Chabad.org
chabad.ca
September 27, 2009
The article:
The article is lacking the fact that the Jewish hour was divided into 1080 parts. Unfortunately, I do not know the source of this fact; would you mind telling me the source of the fact mentioned above.
With many thanks,
mina kuttner
Richmond Hill , canada
chabad.ca
March 2, 2009
why is the jews not using the gregorian calendar
i love this expository chabad. but i wonder why the whole world can not use the conventional gregorian calendar. does it mean the jews see it as inaccurate.
david
abuja, nigeria
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