When is Shavuot?
Unlike all the other Holidays in the Tanach, the Feast of Weeks is not given a fixed calendar date but instead we are commanded to celebrate it at the end of a 50-day period known as "
The Counting of the Omer" (Shavuot being the 50th day).
2 The commencement of this 50-day period is marked by the bringing of the
Omer Offering in the Temple as we read, "And you shall count from the morrow after the Sabbath from the day you bring the Omer [Sheaf] of Waving; seven complete Sabbaths shall you count... until the morrow of the seventh Sabbath you will count fifty days... and you shall proclaim on this very day, it shall be a holy convocation for you " (Lev 23,15-16.21). In late Second Temple times a debate arose between the Boethusians and the Pharisees about whether the "morrow after the Sabbath" [Heb.
Mimohorat Ha-Shabbat] refers to the Sunday during Hag HaMatzot [Feast of Unleavened Bread] or the second day of Hag HaMatzot (i.e. the 16th of Nissan). Like the Boethusians and Ancient Israelites before them, the Karaites count the 50 days of the Omer from the Sunday during Hag HaMatzot and consequentially always celebrate Shavuot on a Sunday.
The Rabbanites claim that in the phrase "the morrow after the Sabbath" the "Sabbath" referred to is the first day of Hag HaMatzot. They argue that this day is referred to as a Sabbath because work is forbidden on it. However, the fact is that the Tanach never calls this day a Sabbath
3 and if we look at the actual commandment in the Torah, this Rabbanite interpretation is untenable. We are commanded in Lev 23,16 "Until the morrow after the seventh Sabbath shall you count fifty days". While the first day of Hag HaMatzot could theoretically be called a Sabbath there is no way the
49th day of the Omer could be called a Sabbath, since (according to the Rabbanite theory) this day is neither a holiday nor a Sabbath. This being so, in the Rabbanite reckoning the 50th day of the Omer (=Shavuot) would
NOT be on "the morrow after the seventh Sabbath" as commanded in Lev 23,16. Instead it would be on the morrow after the 7th Tuesday, Wednesday, or Thursday or whatever day it happened to fall out after (see chart). The only way for the 49th day of the Omer to be a Sabbath, thereby making the 50th day "the morrow after the Sabbath" as commanded in Lev 23,16, is if the 1st day of the Omer is on a Sunday.