The Biblical year begins with the first New Moon after the barley in Israel reaches the stage in its ripeness called Aviv. The period between one year and the next is either 12 or 13 lunar months. Because of this, it is important to check the state of the Barley crops at the end of the 12th month. If the barley is Aviv at this time, then the following New Moon is Hodesh Ha-Aviv ("New Moon of the Aviv"). If the barley is still immature, we must wait another month and then check the barley again at the end of the 13th month.
By convention, a 12-month year is referred to as a Regular Year while a 13th month year is referred to as a Leap Year. This should not be confused with Leap Years in the Gregorian (Christian) Calendar, which involve the "intercalation" (addition) of a single day (Feb. 29). In contrast, the Biblical Leap Year involves the intercalation of an entire lunar month ("Thirteenth Month", also called "Adar Bet"). In general, it can only be determined whether a year is a Leap Year a few days before the end of the 12th Month.
Where is Aviv Mentioned in the Hebrew Bible?
The story of the Exodus relates "This day you are going out in the the month of the Aviv." (Ex 13:4).
To commemorate that we left Egypt in the month of the Aviv, we are instructed to bring the Passover sacrifice and celebrate the Feast of Unleavened Bread (Chag HaMatzot) at this time of year. In Dt 16:1 we are commanded:
"Keep the month of the Aviv and make the Passover (sacrifice) to Yehovah your God at night, because in the month of the Aviv, Yehovah your God took you out of Egypt".
Similarly, we are commanded in Ex 23:15,
"You will keep the Feast of Unleavened Bread; seven days you will eat unleavened bread, as I have commanded you, at the time of the month of the Aviv, because in it you went out of Egypt."
The same is commanded in Ex 34:18,
"You will keep the Feast of Unleavened Bread; seven days you will eat unleavened bread, as have I commanded you, at the time of the month of the Aviv, because in the month of the Aviv you went out of Egypt."
What is Aviv?
Aviv indicates a stage in the development of the barley crops. This is clear from Ex 9:31-32 which describes the devastation caused by the plague of hail:
"And the flax and the barley were smitten, because the barley was Aviv and the flax was Giv'ol. And the wheat and the spelt were not smitten because they were dark (Afilot)."
The above passage relates that the barley crops were destroyed by the hail while the wheat and spelt were not damaged. To understand the reason for this we must look at how grain develops. When grains are early in their development they are flexible and have a dark green color. As they become ripe they take on a light yellowish hue and become more brittle. The reason that the barley was destroyed and the wheat was not is that the barley had reached the stage in its development called Aviv and as a result had become brittle enough to be damaged by the hail. In contrast, the wheat and spelt were still early enough in their development, at a stage when they were flexible and not susceptible to being damaged by hail. The description of the wheat and spelt as "dark" (Afilot) indicates that they were still in the stage when they were deep green and had not yet begun to lighten into the light yellowish hue which characterizes ripe grains. In contrast, the barley had reached the stage of Aviv at which time it was no longer "dark" and at this point it probably had begun to develop golden streaks.
We know from several passages that barley which is in the state of Aviv has not completely ripened, but has ripened enough so that its seeds can be eaten parched in fire. Parched barley was a commonly eaten food in ancient Israel and is mentioned in numerous passages in the Hebrew Bible as either "Aviv parched (Kalui) in fire" (Lev 2,14) or in the abbreviated form "parched (Kalui/ Kali)" (Lev 23:14; Jos 5:11; 1Sam 17:17; 1 Samuel 25:18; 2 Samuel 17:28; Ruth 2:14).
While still early in its development, barley has not yet produced large enough and firm enough seeds to produce food through parching. This early in its development, when the "head" has just come out of the shaft, the seeds are not substantial enough to produce any food. At a later stage, the seeds have grown in size and have filled with liquid. At this point the seeds will shrivel up when parched and will only produce empty skins. Over time the liquid is replaced with dry material and when enough dry material has amassed the seeds will be able to yield "barley parched in fire".
Aviv and the Harvest
The month of the Aviv is the month which commences after the barley has reached the stage of Aviv. 2-3 weeks after the beginning of the month the barley has moved beyond the stage of Aviv and is ready to be brought as the "wave-sheaf offering" (Hanafat HaOmer). The "wave-sheaf offering" is a sacrifice brought from the first stalks cut in the harvest and is brought on the Sunday which falls out during Passover (Chag HaMatzot). This is described in Lev 23:10-11,
"When you come to the land which I give you, and harvest its harvest, you will bring the sheaf of the beginning of your harvest to the priest. And he will wave the sheaf before Yehovah so you will be accepted; on the morrow after the Sabbath the priest will wave it."
From this it is clear that the barley, which was Aviv at the beginning of the month, has become harvest-ready 15-21 days later (i.e by the Sunday during Passover). Therefore, the month of the Aviv can not begin unless the barley has reached a stage where it will be harvest-ready 2-3 weeks later.
That the barley must be harvest-ready 2-3 weeks into the month of the Aviv is also clear from Dt 16:9 which states:
"From when the sickle commences on the standing grain you will begin to count seven weeks."
From Lev 23:15 we know that the seven weeks between Passover (Chag Hamatzot) and Pentecost (Shavuot) begin on the day when the wave-sheaf offering is brought (i.e. the Sunday which falls out during Passover):
"And you shall count from the morrow after the Sabbath, from the day you bring the sheaf of waving; they will be seven complete Sabbaths."
Therefore, the "sickle commences on the standing grain" on the Sunday during Passover, i.e. 2-3 weeks after the beginning of the month of the Aviv. If the barley is not developed enough so that it will be ready for the sickle 2-3 weeks later, then the month of the Aviv can not begin and we must wait till the following month.
It should be noted that not all the barley ripens in the Land of Israel at the same time. The wave-sheaf offering is a national sacrifice brought from the first fields to become harvest-ready. However, the first-fruit offerings brought by individual farmers can vary in ripeness anywhere from "Aviv parched in fire" to fully ripe grain which may be brought "crushed" or "coarsely ground". This is what is meant in Lev 2:14,
"And when you bring a first-fruit offering to Yehovah; you shall bring your first-fruit offering as Aviv parched in fire or crushed Carmel" (Carmel is grain which has hardened beyond Aviv to the point where it can be "crushed" or "coarsely ground").
All of the above passages have been translated directly from the Hebrew and it is worth noting that the King James translators seem to have only understood the various Hebrew agricultural terms very poorly. In Lev 2:14 they translated Carmel as "full ears" and "Aviv" as "green ears" whereas in Lev 23:14 they translated Carmel as "green ears"!
In summation, barley which is in the state of Aviv has 3 characteristics:
- It is brittle enough to be destroyed by hail and has begun to lighten in color (it is not "dark").
- The seeds have produced enough dry material so it can be eaten parched.
- It has developed enough so that it will be harvest-ready 2-3 weeks later.