The Torah states that the Omer offering (i.e., the first day of counting the Omer) is the first day of the barley harvest (Deut. 16:9
). It should begin "on the morrow after the Shabbat
", and continue to be counted for seven Sabbaths. (Lev. 23:11
). The Talmudic Sages determined that "Shabbat" here means a day of rest and refers to the first day of Passover. Thus, the counting of the Omer begins on the second day of Passover and continues for the next 49 days, or seven complete weeks, ending on the day before Shavuot.
According to this calculation, Shavuot will fall on the day of the week after that of the first day of Passover (e.g., if Passover starts on a Thursday, Shavuot will begin on a Friday).
Most secular scholarship, and the Karaites
, as well as Catholics
and the historical Sadducees
, dispute this interpretation. They infer the "Shabbat" referenced is the weekly Shabbat. Accordingly, Shavuot falls on the day after the weekly shabbat, counting from seven weeks since the day after the first shabbat during Pesach.
This interpretation was shared by the 2nd-century BCE author of the Book of Jubilees
who was motivated by the priestly sabbatical solar calendar
of the 3rd and 2nd centuries BCE, which was designed to have festivals and Sabbaths fall on the same day of the week every year. On this calendar (best known from the Book of Luminaries in 1 Enoch
), Shavuot fell on the 15th of Sivan, a Sunday. The date was reckoned fifty days from the first Sabbath
(i.e. from the 25th of Nisan). Thus, Jub. 1:1 claims that Moses ascended Mount Sinai
to receive the Torah "on the sixteenth day of the third month in the first year of the Exodus of the children of Israel from Egypt".