Counting the Omer.

 

By

 

Yochanan Zaqantov

 

Counting the Omer is the requirement for the setting of Feast of Weeks (Chag HaShavu’ot).  By counting we establish when this day is.  This is the only Chag we count to determine.  We are also commanded to count the days and weeks.  We will look at the texts concerning this and determine where we start counting from.

 

The word in Hebrew used for the Sheaf is Omer.  Omer (Ayin-Mem-Resh) is reference number 6016.  Which is a masculine noun and from the verb ‘Amar or bound sheaf and is reference number 6014.

 

How do we know Omer means sheaf?

 

Ruth 2:7, 15

 

7     She said, ‘Please let me glean and gather among the sheaves (ba’omarim) behind the reapers.’ She has been on her feet ever since she came this morning. She has rested but little in the hut.”

 

15     When she got up again to glean, Boaz gave orders to his workers, “You are not only to let her glean among the sheaves (ha’omarim), without interference,

 

 

7 וַתֹּאמֶר אֲלַקֳטָה־נָּא וְאָסַפְתִּי בָעֳמָרִים אַחֲרֵי הַקּוֹצְרִים וַתָּבוֹא וַתַּעֲמוֹד מֵ‍אָז הַבֹּקֶר וְעַד־עַתָּה זֶה שִׁבְתָּהּ הַבַּיִת מְעָט׃

15 וַתָּקָם לְלַקֵּט וַיְצַו בֹּעַז אֶת־נְעָרָיו לֵאמֹר גַּם בֵּין הָעֳמָרִים תְּלַקֵּט וְלֹא תַכְלִימוּהָ׃

 

Here we see that in the Plural form that many sheaves are Amarim.  Whereas in the next verse we see that it is omer in the singular.

 

Devarim/Deuteronomy 24:19

 

19     When you reap the harvest in your field and overlook a sheaf (omer) in the field, do not turn back to get it; it shall go to the stranger, the fatherless, and the widow—in order that Yehovah Eloheykha may bless you in all your undertakings.

9 כִּי תִקְצֹר קְצִירְךָ בְשָׂדֶךָ וְשָׁכַחְתָּ עֹמֶר בַּשָּׂדֶה לֹא תָשׁוּב לְקַחְתּוֹ לַגֵּר לַיָּתוֹם וְלָאַלְמָנָה יִהְיֶה לְמַעַן יְבָרֶכְךָ יְהוָה אֱלֹהֶיךָ בְּכֹל מַעֲשֵׂה יָדֶיךָ׃

 

 

So we can see that the omer they refer to in Leviticus 23 is the sheaf from the first harvest.  Not necessarily a measure of Barley.

 

Vayiqra / Leviticus 23:9-16

 

9     Yehovah spoke to Moshe, saying: 10     Speak to the Israelite people and say to them:

When you enter the land that I am giving to you and you reap its harvest, you shall bring the first sheaf of your harvest to the priest. 11     He shall elevate the sheaf before Yehovah for acceptance in your behalf; the priest shall elevate it on the day after the sabbath. 12     On the day that you elevate the sheaf, you shall offer as a burnt offering to Yehovah a lamb of the first year without blemish. 13     The meal offering with it shall be two-tenths of a measure of choice flour with oil mixed in, an offering by fire of pleasing odor to Yehovah; and the libation with it shall be of wine, a quarter of a hin. 14     Until that very day, until you have brought the offering of Eloheykha, you shall eat no bread or parched grain or fresh ears; it is a law for all time throughout the ages in all your settlements.

15     And from the day on which you bring the sheaf of elevation offering—the day after the sabbath—you shall count off seven weeks. They must be complete: 16     you must count until the day after the seventh week—fifty days; then you shall bring an offering of new grain to Yehovah.

 

Let us examine this text here to understand what it is telling in English really reflects what is said in Hebrew.

 

9 And spoke Yehovah to Mosheh to say,

 

10 Speak to Sons of Yisrael and you say to them when you come to the land, which I give to you reap/shorten it harvest and have brought in sheaf (omer) of the beginning of your harvest to the priest.

 

11 And He shall wave the sheaf (ha’omer) before Yehovah for your acceptance on the morrow of the Shabbat shall wave it the priest.

 

12 And shall prepare you in the day you wave the Sheaf (ha’omer) a ram, a whole one [no blemish], a son of a year, for a burnt offering to Yehovah.

 

13 And its food offering two tenths of flour mixed with oil, a fire offering to Yehovah a fragrance soothing and its drink offering, of wine a fourth of a hin.

 

14 And bread or roasted grain or carmel (fully ripe) not eat you until same day this until brought you the offering of Eloheykhem a statue for all time to your generations in all dwellings yours.

 

15 And you shall number/count to you on the morrow the shabbat from the day you bring the Sheaf of the wave offering seven Shabbatot whole they shall be.

 

16 Until on the morrow the shabbat seventh, you shall number/count fifty days.  And you shall bring a food offering (min’chah) new to Yehovah.

9 וַיְדַבֵּר יְהוָה אֶל־מֹשֶׁה לֵּאמֹר׃

10 דַּבֵּר אֶל־בְּנֵי יִשְׂרָאֵל וְאָמַרְתָּ אֲלֵהֶם כִּי־תָבֹאוּ אֶל־הָאָרֶץ אֲשֶׁר אֲנִי נֹתֵן לָכֶם וּקְצַרְתֶּם אֶת־קְצִירָהּ וַהֲבֵאתֶם אֶת־עֹמֶר רֵאשִׁית קְצִירְכֶם אֶל־הַכֹּהֵן׃

11 וְהֵנִיף אֶת־הָעֹמֶר לִפְנֵי יְהוָה לִרְצֹנְכֶם מִ‍מָּחֳרַת הַשַּׁבָּת יְנִיפֶנּוּ הַכֹּהֵן׃

12 וַעֲשִׂיתֶם בְּיוֹם הֲנִיפְכֶם אֶת־הָעֹמֶר כֶּבֶשׂ תָּמִים בֶּן־שְׁנָתוֹ לְעֹלָה לַיהוָה׃

13 וּמִנְחָתוֹ שְׁנֵי עֶשְׂרֹנִים סֹלֶת בְּלוּלָה בַשֶּׁמֶן אִשֶּׁה לַיהוָה רֵיחַ נִיחֹחַ וְנִסְכֹּה יַיִן רְבִיעִת הַהִין׃

14 וְלֶחֶם וְקָלִי וְכַרְמֶל לֹא תֹאכְלוּ עַד־עֶצֶם הַיּוֹם הַזֶּה עַד הֲבִיאֲכֶם אֶת־קָרְבַּן אֱלֹהֵיכֶם חֻקַּת עוֹלָם לְדֹרֹתֵיכֶם בְּכֹל מֹשְׁבֹתֵיכֶם׃ ס

15 וּסְפַרְתֶּם לָכֶם מִ‍מָּחֳרַת הַשַּׁבָּת מִ‍יּוֹם הֲבִיאֲכֶם אֶת־עֹמֶר הַתְּנוּפָה שֶׁבַע שַׁבָּתוֹת תְּמִימֹת תִּהְיֶינָה׃

16 עַד מִ‍מָּחֳרַת הַשַּׁבָּת הַשְּׁבִיעִת תִּסְפְּרוּ חֲמִשִּׁים יוֹם וְהִקְרַבְתֶּם מִנְחָה חֲדָשָׁה לַיהוָה׃

 

 

The points to consider from this section is:

 

  1. What is the morrow?
  2. Why use Shabbatot and not Shavu’ot?
  3. Which morrow after the Shabbat?
  4. We are not to eat of the new grain or roast grain until the sheaf is waved.
  5. We are to count both complete Shabbats and days.

 

So let’s look at what is the Morrow.

 

Morrow in Hebrew is Macharat. It is reference number 4283 and is a feminine noun.  The Hebrew is Mem-Chet-Resh-Tav.  It os from the verb root Mem-Chet-Resh which is Machar and reference number 4279.  The verb mean “to morrow” or towards morrow.  The feminine noun is morrow so as a thing it is a specific obect.  In this case it is a time of day.

 

We can see that this is the period after sunrise.

 

Yonah/Jonah 4:7

 

6     Yehovah Elohim provided a ricinus plant, which grew up over Jonah, to provide shade for his head and save him from discomfort. Jonah was very happy about the plant. 7     But the next day at dawn (ba’olot hashachar lamacharat - in the rising of dawn of the morrow בַּעֲלוֹת הַשַּׁחַר לַמָּחֳרָת) Elohim provided a worm, which attacked the plant so that it withered.

 

We also see that the rising was early the morrow.

 

Shemot/Exodus 32:6

 

5     When Aaron saw this, he built an altar before it; and Aaron announced: “Tomorrow (machar 4279  מָחָר) shall be a festival of Yehovah!” 6     Early next day (vayash’kiymu mimacharat - And rose up in the morrow וַיַּשְׁכִּימוּ מִ‍מָּחֳרָת), the people offered up burnt offerings and brought sacrifices of well-being; they sat down to eat and drink, and then rose to dance.

 

Here again we see that the Morrow is referring to a day light portion of the day follow another daylight period or the evening.

 

Shofetim/Judges 6:38

 

37     here I place a fleece of wool on the threshing floor. If dew falls only on the fleece and all the ground remains dry, I shall know that You will deliver Israel through me, as You have said.” 38     And that is what happened. Early the next day (vayash’kem mimacharat וַיַּשְׁכֵּם מִ‍מָּחֳרָת), he squeezed the fleece and wrung out the dew from the fleece, a bowlful of water.

 

Shemu’el Aleph/1 Samuel 5:3-4

 

3     Early the next day, the Ashdodites (vayash’kimu ash’dodim mimacharat וַיַּשְׁכִּמוּ אַשְׁדּוֹדִים מִ‍מָּחֳרָת) found Dagon lying face down on the ground in front of the Ark of Yehovah. They picked Dagon up and put him back in his place; 4     but early the next morning (vayash’kimu baboqer mimacharat וַיַּשְׁכִּמוּ בַבֹּקֶר מִ‍מָּחֳרָת), Dagon was again lying prone on the ground in front of the Ark of Yehovah. The head and both hands of Dagon were cut off, lying on the threshold; only Dagon’s trunk was left intact.

 

So we see from this that the morrow after the Shabbat is the daylight portion of the day following the period referenced..

 

So after the Shabbat ends the next morning is the morrow.  So that leaves us with a question.  What Shabbat is it?

 

Well according to our brothers the Rabbanites the Shabbat is the first day of Chag HaMatzot (Feast of Unleavened Bread).  The reasoning for this is that since work is restricted on that day save cooking then it must also be a Shabbat since working forbidden on Shabbat.  They don’t make the leap that cooking; as work would also be forbidden on Shabbat so therefore they are not the same.  They are using analogy to make the first and last days of the Feast Shabbats or Shabbatot.  So they start the count of the Omer on the morrow of the first day of unleavened bread.  So in the references to the first and seventh day of Chag HaMatzot does it ever refer to them as Shabbatot/Sabbaths?  Let’s look at… 

 

Vayiqra/Levitucus 23:4-8

 

4     These are the set times (mo’adey מוֹעֲדֵי) of Yehovah, the sacred occasions (miqra qodesh מִקְרָאֵי קֹדֶשׁ), which you shall celebrate each at its appointed time (bamo’adam בְּמוֹעֲדָם): 5     In the first month, on the fourteenth day of the month, at twilight, there shall be a passover offering to Yehovah, 6     and on the fifteenth day of that month Yehovah’s Feast of Unleavened Bread. You shall eat unleavened bread for seven days. 7     On the first day you shall celebrate a sacred occasion (miqra qodesh מִקְרָאֵי קֹדֶשׁ): you shall not work at your occupations. 8     Seven days you shall make offerings by fire to Yehovah. The seventh day shall be a sacred occasion (miqra qodesh מִקְרָאֵי קֹדֶשׁ): you shall not work at your service work..

 

Notice that Shabbat nor Shabbaton are used here while later in the same chapter the word Shabbaton is used for Yom Teru’ah, Yom Hakippurim, and the First and Eighth of Sukkot.

 

24     Speak to the Israelite people thus: In the seventh month, on the first day of the month, you shall observe complete rest (sshabbaton), a sacred occasion (miqra qodesh) commemorated with loud blasts. (Yom Teru’ah)

 

32     It shall be a sabbath of complete rest (shabbaton) for you, and you shall practice self-denial; on the ninth day of the month at evening, from evening to evening, you shall observe this your sabbath. (Yom Hakippurim)

 

39     Mark, on the fifteenth day of the seventh month, when you have gathered in the yield of your land, you shall observe the festival of Yehovah [to last] seven days: a complete rest (shabbaton) on the first day, and a complete rest (shabbaton) on the eighth day. (Sukkot and the eighth day)

 

So you can see that here we see that the end of the growing season the miqra qodesh or mo’adey (appointed times) are Shabbaton or/ Shabbat whereas the beginning of the growing season the miqra qodesh or mo’adey are not.  This is the only place were we see the word Shabbaton used in reference to a miqra qodesh.  Therefore, we see that the only Shabbat possible in the one that occurs in conjunction with the weekly Shabbat and the Chag HaMatzot.

 

How do we know this was to happen during the Feast of Unleavened Bread?

 

Yehoshua/Joshua 5:10-12

 

10     Encamped at Gilgal, in the steppes of Jericho, the Israelites offered the passover sacrifice on the fourteenth day of the month, toward evening (should be “in evening”).

11     On the day after (mimacharat - on the morrow מִ‍מָּחֳרַת) the passover offering, on that very day, they ate of the produce (me’ovur  מֵ‍עֲבוּר) of the country, unleavened bread (matzot) and parched grain (va qalui/kalui – roasted grain וְקָלוּי). 12     On that same day, when they ate of the produce (me’ovur  מֵ‍עֲבוּר) of the land, the manna ceased. The Israelites got no more manna; that year they ate of the yield of the land of Canaan.

 

Mimacharat was the morrow after the Pesach which was the previous evening.  We know from this that the next morning was the Morrow and so the first day of Unleavened Bread occurred on the first day of the week after Shabbat.  Therefore, the first day of the unleavened bread can not be a Shabbat.  This is because they are to bring the offering the morrow of the Shabbat.  If the first day was a Shabbat they would have brought it the next day.  We know that they ate of the produce of the land in the day period after the Pesach offering which would have been the 15th day.  We know it is the day period of the 15th from the verse used in Numbers 33:3

 

Bamidbar /Numbers 33:3

 

3 They set out from Rameses in the first month, on the fifteenth day of the first month. It was on the morrow (mimacharat מִ‍מָּחֳרַת) of the Passover (hapesach הַפֶּסַח) [offering] that the Israelites started out defiantly, in plain view of all the Egyptians.

 

This is the first day of Unleavened Bread.  We know that they were instructed to make an offering before eating it.  This was from the words spoken by Moshe and so Joshua would have been well aware of it. 

 

Vayiqra / Leviticus 23:9-11

 

9     Yehovah spoke to Moshe, saying: 10     Speak to the Israelite people and say to them:

When you enter the land that I am giving to you and you reap its harvest, you shall bring the first sheaf (omer) of your harvest to the priest. 11     He shall elevate the sheaf (ha’omer) before Yehovah for acceptance in your behalf; the priest shall elevate it on the day after the Sabbath (mimacharat haShabbat  מִ‍מָּחֳרַת הַשַּׁבָּת).

 

Joshua/Yehoshua would have done this with the Children/Benei of Yisrael.  Here we have the Shabbat, which falls outside the 7 days of Chag Hag Matzot.  With the 15 day as the morrow of the Shabbat, which shows us also that, the important day to fall within the seven days is the Morrow of the Shabbat.  This would also be the day of the first count.  It also shows us that it is not a shabbat and the first day are not the same less they would have eaten unleavened bread of the land on the 16th not the 15th.

 

Old Grain verses Aviv

 

Some have reasoned that me’ovur which in the JPS is listed as produce of the land is old grain because the meaning is to pass through.  Thus, this means the grain was old.  If this was truly the case then then they would have roasted the grain since they needed to make unleavened bread.  Kar’mel is the term used for the harvest ready produce for grain and other crops.  Thus, if the only thing they needed was old grain to grind then why roast the grain.  If you are going to eat them as seeds roasted then yes they could roast old grain.  But the question is whether this is referring to old grain.

 

Eychah/Lamentaions 3:44

 

44     You have screened Yourself off with a cloud, That no prayer may pass through (me’ovur מֵ‍עֲבוֹר).

 

The reason I show this that this place shows it as pass through.  Thus Prayer may not pass through.  The verb from which this word is derived is עָבַר.  The reference for this is 5674.  Thus, it is the noun which reflects the passing through and not a grain which is made ripe.  Also there is only two other places this word is used and that is Yehoshua/Joshua 5:11-12.

 

11     On the day after (mimacharat - on the morrow מִ‍מָּחֳרַת) the passover offering, on that very day, they ate of the produce (me’ovur  מֵ‍עֲבוּר) of the country, unleavened bread (matzot) and parched grain (va qalui/kalui – roasted grain וְקָלוּי). 12     On that same day, when they ate of the produce (me’ovur  מֵ‍עֲבוּר) of the land, the manna ceased. The Israelites got no more manna; that year they ate of the yield of the land of Canaan.

In the Hebrew it states: וַיֹּאכְלוּ מֵ‍עֲבוּר הָאָרֶץ

 

Another way of translating this is ‘and they ate passing through the land”.  Thus, this has nothing to do with grain but that they were passing through the land.  There is no indication of Kar’mel nor Aviv.  The reason is I state that they ate Aviv is because of the firstfruit offering which is told in Vayiqra/ Leviticus 2:14

 

14     If you bring a meal offering (minchah) of first fruits to Yehovah, you shall bring new ears (Aviv) parched (Qalui) with fire, grits (pounded) of the fresh grain (Karmel), as your meal offering of first fruits.

 

Thus, Karmel for the Offering of the Bikkurey (First Fruits) is prepared in this manner.  First the Waving of the Sheaf is done as commanded.

 

Vayiqra / Leviticus 23:9-16

 

9     Yehovah spoke to Moshe, saying: 10     Speak to the Israelite people and say to them:

When you enter the land that I am giving to you and you reap its harvest, you shall bring the first sheaf of your harvest to the priest. 11     He shall elevate the sheaf before Yehovah for acceptance in your behalf; the priest shall elevate it on the day after the sabbath. 12     On the day that you elevate the sheaf, you shall offer as a burnt offering to Yehovah a lamb of the first year without blemish. 13     The meal offering with it shall be two-tenths of a measure of choice flour with oil mixed in, an offering by fire of pleasing odor to Yehovah; and the libation with it shall be of wine, a quarter of a hin. 14     Until that very day, until you have brought the offering of Eloheykha, you shall eat no bread (lechem) or parched grain (Qali) or fresh ears (Karmel); it is a law for all time throughout the ages in all your settlements.

15     And from the day on which you bring the sheaf of elevation offering—the day after the sabbath—you shall count off seven weeks. They must be complete: 16     you must count until the day after the seventh week—fifty days; then you shall bring an offering of new grain to Yehovah.

 

The second new grain offering is Wheat.  The Qali is roasted of Aviv grain.  It would be in the Sheaf still.  Where as old grain would be processed and stored without stalks. They do not store sheafs.

 

So is this just new Qaraite thinking or has this been the thoughts of previous Qaraite Scholars.

 

Samuel Al-Magribi wrote his work on this in 1434 in Arabic.  In the Karaite Anthology, Pages 215-218, he addresses waving the Sheaf.  In this reference, he states that the Day after the Shabbat must fall within the Days of Unleavened Bread.  His reasoning is the verses I have shown here Joshua 5:11 and Numbers 33:3.  He also links this to Lev. 23:14. 

 

In the counting of the omer the Karaite interpretation of ממחרת השבת (Lev. XXII 11) is given by the formula for the first day of the counting, היום יום

ראשון לשבוע ראשון וגוי, which is repeated with appropriate substitutions at the beginning of each of the seven weeks.  (Karaite Siddur, pg 88-90)

http://books.google.com/books?id=e9fnAAAAIAAJ&lpg=PA104&dq=omer%20karaite&pg=PA104#v=onepage&q=omer%20karaite&f=false

 

The counting of the Omer after the Morrow of the Shabbat is captured in many books on Karaite Literature.

 

In the book,”The Jewish Festivals: from their beginnings to our own day” by Hayyim Schauss who states:

 

“It says only that it is to be celebrated fifty days after the offering of the omer, the first sheaf of the barley harvest, which was to be offered on ‘the morrow after the Shabbat.’  Thus, the Sadducces, the party of conservative priest, interpreted this as meaning the omer was to be offered the first Sunday of Pesach, and that Shovuos (Shavuot), therefore, would always fall on the seventh Sunday after Pesach.” (Schauss, pg. 87)

 

Clearly, the Sadduces who were Priests and were to teach the law would have taught this method before modern Karaites. Often the Karaites are accused of being from the Sadducces because of the similarity of beliefs.

 

Another place we find the reference to counting is:

 

Devarim / Deuteronomy 16: 9-10

 

9     You shall count off seven weeks; start to count the seven weeks when the sickle is first put to the standing grain. 10     Then you shall observe the Feast of Weeks for Yehovah Eloheykha, offering your freewill contribution according as Yehovah Eloheykha has blessed you.

 

9 Seven Weeks (shavu’ot) you shall number/count for you from begin the sickle the standing grain begin you to number seven (weeks) shavu’ot. 

 

10 And perform you the Feast of Weeks (Shavu’ot) to Yehovah Eloheykha enough a voltive offering  you hand which you give according as blesses you Yehovah Eloheykha.

9 שִׁבְעָה שָׁבֻעֹת תִּסְפָּר־לָךְ מֵ‍הָחֵל חֶרְמֵשׁ בַּקָּמָה תָּחֵל לִסְפֹּר שִׁבְעָה שָׁבֻעוֹת׃

10 וְעָשִׂיתָ חַג שָׁבֻעוֹת לַיהוָה אֱלֹהֶיךָ מִסַּת נִדְבַת יָדְךָ אֲשֶׁר תִּתֵּן כַּ‍אֲשֶׁר יְבָרֶכְךָ יְהוָה אֱלֹהֶיךָ׃

 

Notice here the word weeks is used.  Shavu’ot is used here because he is reminding them of the previous reference in Leviticus.  That way they could count the weeks by counting Shabbatot/Sabbaths.  Each week would end in a Shabbat as it does weekly.

 

So we need to count from the morrow after the Shabbat that falls during the Feast of Unleavened Bread.  From the Joshua account, that day would be the first day of the week which in Hebrew is Yom Rishon and the in the Gregorian calendar as Sunday.  Counting the individual days up to 49 and the weeks up to 7 complete shabbatot we then keep Chag HaShavu’ot on the first day of the week as we started the counting from.

 

So how will we count it this year?

 

For 2010 the count will be:

 

April 17

April 18 Pesach in Erev

April 19 FDUB

April 20

April 21

April 22

April 23 Shabbat

April 24 Day 1 Week 1

Morrow after shabbat

April 25 Day 2 Week 1 LDUB

April 26 Day 3 Week 1

 

April 27 Day 4 Week 1

April 28

Day 5 Week 1

April 29

Day 6

Week 1

April 30

Day 7 Week 1

May 1 Day 8

Week 2

May 2  Day 9 Week 2

May 3

Day 10 Week 2

May 4

Day 11 Week 2

May 5

Day 12 Week 2

May 6

Day 13 Week 2

May 7

Day 14 Week 2

May 8

Day 15 Week 3

May 9

Day 16 Week 3

May 10

Day 17 Week 3

May 11

Day 18 Week 3

May 12

Day 19 Week 3

May 13

Day 20 Week 3

May 14

Day 21 Week 3

May 15 Day 22 Week 4

May 16

Day 23 Week 4

May 17 Day 24 Week 4

May 18 Day 25 Week 4

May 19 Day 26 Week 4

May 20 Day 27 Week 4

May 21 Day 28 Week 4

May 22 Day 29 Week 5

May 23 Day 30 Week 5

May 24 Day 31 Week 5

May 25

Day 32 Week 5

May 26 Day 33 Week 5

May 27 Day 34 Week 5

May 28 Day 35 Week 5

May 29 Day 36 Week 6

May 30

Day 37 Week 6

May 31

Day 38 Week 6

June 1

Day 39 Week 6

June 2

Day 40 Week 6

June 3

Day 41 Week 6

June 4

Day 42 Week 6

June 5

Day 43 Week 7

June 6

Day 44 Week 7

June 7

Day 45 Week 7

June 8

Day 46 Week 7

June 9

Day 47 Week 7

June 10

Day 48 Week 7

June 11

Day 49 Week 7

June 12

Day 50

Morrow after  7th Shabbat

 

 

 

 

 

 

 

It is very important that we read the Tanakh for our answers and not seek out convoluted reasons for not keeping it in its appointed time.  It is not kept outside the Days of Unleavened Bread nor do equinoxes or stars determine it.  Its tied is to the Barley Harvest, which starts during the Days of Unleavened Bread and continues seven Shabbatot to the Wheat Harvest.  For the Harvest to begin in the Land it must be ready for harvesting.  If the month does not get called with the Aviv then it will not be harvestable ready by the time of the Omer/Sheaf that is waved as a offering.