The Jewish calendar was ingeniously constructed to regulate all the secular affairs of the people, as well as to mark the proper time for observing the recurring religious feasts and holy days. It is established on both a lunar and solar basis, meaning that both the moon and sun affect its structure, as we shall shortly observe.

Genesis specifically states that the heavenly bodies were divinely ordained to carry out a timekeeping function: days and years to be measured by the sun, months by the moon, and cycles by the stars (Genesis 1:14). In sharp contrast to other ancient calendars, the Jewish week ran consecutively in a seven day cycle completely independent of the lunar or solar cycles. Thus it was patterned on the Creation account of seven days’ duration and permitted a multiplication of cycles of seven for various religious convocations and festivals.

First, let us note how the moon’s motion is used as the basis of the Jewish month. The moon, earth’s sole satellite, revolves about it in just 29 days, 12 hours, 44 minutes, and 3 1/3 seconds on the average, or about 29.53 days. To closely approximate this, and to keep the months of the Jewish calendar a whole number of days, the Jewish months were made to alternate between 29 and 30 days. This becomes the unvarying rule, with every Jewish month being either 29 or 30 days in length. But only in what is termed a “normal ordinary” year do these days alternate perfectly with each other throughout the course of the year i.e. -30, 29, 30, 29, 30, 29, etc.).

The names of the Jewish months and their order are shown in the following table, entitled “Synchronized Jewish Calendar.” The names were originally borrowed by the ancient Israelites from their Canaanite or Phoenician neighbors. That the names had seasonal connotations is easily shown from the four that survived in the Biblical records. Abib, corresponding to Nissan, means “month of the ripening ears,” Ziv (Iyar) means “month of flowers,” Ethanim (Tishri) means “month of perennial streams” and Bul (Heshwan) means “rain or showers.” We recall from the account in Exodus 12:2 that it was Jehovah God who required Moses to begin the sacred Jewish year with the month Abib (early in the spring), commencing with the institution of the Passover. This practice would have helped to set the Israelites apart from the heathen nations round about.

SYNCHRONIZED JEWISH CALENDAR

Sacred Order	Civic Order Names of Months			Farming Season
7	1	TISHRI	(Sep-Oct)	Early rains, plowing
8	2	HESHWAN	(Oct-Nov)	Wheat & barley sowing
9	3	KISLEV	(Nov-Dec)	Winter season –
10	4	TEBET	(Dec-Jan)	– Rainy period
11	5	SHEBAT	(Jan-Feb)	Trees blooming
12	6	ADAR	(Feb-Mar)	Almond blooming
		V-ADAR
1	7	NISSAN	(Mar-Apr)	Barley harvest
2	8	IYAR	(Apr-May)	Barley harvest
3	9	SIVAN	(May-Jun)	Wheat harvest
4	10	TAMUZ	(Jun-Jul)
5	11	AB	(Jul-Aug)	Grape, fig & olive ripen
6	12	ELUL	(Aug-Sep)	Vintage

 

Next we should note how the apparent motion of the sun is used as the basis of the Jewish year (as distinguished from the Jewish month).

The expression “solar year” refers to the time required for the planet earth to make one complete orbit about the sun in its never-ending celestial journey. This has been determined to be 365 days, 5 hours, 48 minutes, and 46 seconds, or about 365.24 days.

To maintain a fixed relationship between the Jewish holidays and the seasons of the year, it was necessary to adopt the solar year as the basis for the Jewish year (and again we emphasize the word “year”). A “normal ordinary” Jewish year consists of 12 months alternating between 29 and 30 days, as we have stated. This aggregates 354 days as a near approximation of 12 lunar months, or a “lunar year,” the length of which is actually about 354.37 days.

But 12 lunar months are less than the solar year by 10 days, 21 hours, 0 minutes, and 6 seconds, which, if carried over from year to year, would cause each Jewish year to begin almost 11 days earlier in the solar year than its predecessor. Under this arrangement, Passover, for example, which is fixed as a spring holiday, would recede first into winter, then into autumn, and so on. To adjust for these differences and to prevent a wandering of the special holidays which were meant to be fixed according to the season, a thirteenth month was added to certain Jewish years, called leap years. Thus the addition of the thirteenth month, called “V-Adar” or an intercalary month, assists in keeping the Jewish year in closer accord with the solar years.

Basic to the structure of the Jewish calendar is a nineteen year cycle consisting of twelve “Ordinary” (12 month) years and seven “Leap” (13 month) years. Leap years occur in the 3rd, 6th, 8th, 11th, 14th, 17th, and 19th years of the 19-year cycle. The 13th month, named “V-Adar,” has 29 days and is interposed between Adar and Nissan. Also, the month of Adar is increased from 29 to 30 days in every leap year. By these and other adjustments, the accumulated time of the Jewish “19-year cycle” is almost exactly equivalent to a corresponding number of solar years and thus maintains a fixed relationship between them. (The difference is only about two hours in any given 19-year cycle.)

Overall there are six basic types of years in the Jewish calendar. Each of the “ordinary” and “leap” years previously described is further divided into “deficient”,”normal,” or “full,” because some years are decreased by one day and others are increased by a day. The six types of the Jewish year are enumerated in the following table. They are described as “deficient ordinary,” “normal ordinary,” “deficient leap,” “full leap” and so on.

SIX TYPES OF THE JEWISH YEAR

Deficient	Ordinary Years 353 days	Leap Years 383 days
Normal	354	384
Full	355	385

 

There is a fixed relationship between the Jewish and Gregorian (general or common) Calendar. By definition, Jewish Year I was designated as having begun in the autumn of the year 3761 BC. This is taken to represent both the date of Creation and the starting point for reckoning all events according to the Jewish Calendar.

Thus the Jewish year is always numerically greater than its corresponding General year by the number 3,761. However, since the Jewish (civic) year begins in the autumn with Tishri 1, every Jewish year laps portions of two General years (and conversely every General year laps portions of two Jewish years). This is shown in the diagram following, and serves to complicate somewhat the conversions from one system to another. But the rules for conversion are readily available.

The following equivalencies serve to illustrate conversions from Jewish to General (Gregorian) years:

Nissan 15 in Jewish year 5741 falls in 1981 AD

Nissan 15 in Jewish year 6000 falls in 2240 AD

 

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References

Tenney, Merrill C. (ed.). ‘I’he Zondervan Pictorial Bible Dictionary. Grand Rapids, Mich.: Zondervan Publishing House, 1963.

Zinberg, George. Jewish Calendar Mystery Dispelled. New York: Vantage Press, 1963.

– Contributed

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