There is a Rabbinical tradition called "counting the omer." In this tradition, you begin counting from the day after the first day of Pesach (Passover). For instance, if the first day of Pesach is on April 15 (as it is in 2014), then the first day of the count for the omer is on April 16. Then you count day 2 all the way to the 50th day, which would be Shavuot (Pentecost), which would be on June 4.
An omer is a dry measure equal to a little more than 2 quarts, or in biblical measure, a tenth of an ephah. In this particular case, it is an omer of barley. This quaint custom of "counting the barley" isn't biblical. For one thing, I don't know anyone who would have 50 omers of barley to count, other than a farmer who might be growing barley. In a period of 50 days, that would mean having at least 100 quarts of barley on hand for the counting.
Biblically, we are to count the days, not the omer. Also, the count does not begin on the day after the first day of Passover. In Leviticus 23:11, the Israelites were com-manded to wave a sheaf (of barley) "on the day after the Sabbath" that occurred during Passover. The day after the Sabbath is Yom Rishon ("Sunday"). Then in Levicus 23:15, we are commanded to "count for yourselves from the say after the Sabbath (that occurs during Passover), from the day when you brought in the sheaf of the wave offering. There shall be seven complete Sabbaths." There is no com-mandment to count omers of barley. We are to count the days, not any omers of barley. And we begin this count from the day after the Shabbat that occurs during Passover, not from the day after the first day of Passover.
Then in Leviticus 23:16, we read, "You shall count fifty days to the day after the seventh Sabbath. Then you shall present a new grain offering to YHWH (the LORD)." The day "after the seventh Sabbath" would always be on a Sunday. As most of you know, Shabbat begins at sunset on Friday and ends at sunset on Saturday. Shavuot would therefore begin at sunset on Saturday, and end 24 hours later at sunset on Sunday.
However, with the Rabbinic count, Shavuot could be on any day of the week. I can understand that the first day of Passover is also a Sabbath, that is, a Holy Day Sabbath. In this particular case (2014), the count would begin on a Wednesday, and end on a Wednesday. However, the Scriptures tell us to end the count on the day after the seventh Shabbat. Therefore, regardless of which day you use to begin the count, the count should end on the day after the seventh Shabbat.
In 2014, the Biblical count would begin on the day after the Shabbat that occurs during Passover, which in 2014 is April 19. You then begin counting the days on Yom Rishon (Sunday April 20). You then begin counting to the 50th day, which which begins at sunset on Saturday June 7, and ends on Sunday June 8 in 2014.
The Rabbinic reckoning comes to us from the P'rushim (Pharisees). We have great respect for both the Pharisees and the Rabbis. However, in this particular case, they are wrong. The Sadducees always observed Sha-vuot (Pentecost) on "Sunday," as we do. The Sadducees got a lot of things wrong. They didn't believe in angels or the resurrection of the dead, but they got this one right! Also, the Karaite Jews observe the Biblical reckoning for Shavuot on Sunday. Christians observe "Pente-cost Sunday." Even the Christians got this one right! We give credit where credit is due!
Many in the Messianic Jewish community observe Shavuot according to the Rabbinic reckoning, which can occur on any day of the week. Perhaps you also follow the Rabbinic reckoning. I have no problem with that. At least you are observing Shavuot!
Shavuot may have been primarily an agricultural festival 2000 years ago, as the first fruits of the wheat harvest. However, the Rabbis noticed that the Torah was given in the third month. The first month of the Sacred calendar begins in the springtime, the month of Aviv (Nissan), then the month of Iyyar, and then the third month, Sivan. Exodus 19:1 lets us know that the Aseret HaD'varim (Ten Sayings, or Ten Commandments) were given in this month, in all likelihood, on Shavuot. For this reason, Shavuot is considered the birthday of Judaism. The Ruach HaKodesh (Holy Spirit) was poured out on Yeshua's talmidim (disci-ples) on Shavuot in Acts chapter 2. We cel-ebrate it as the birth of Messianic Judaism!