9b----------------------------------------9b

1) DETERMINING THE YEAR OF THE "CHURBAN" AND THE YEAR OF "SHEMITAH"
QUESTION: The Gemara quotes Rav Huna brei d'Rav Yehoshua who teaches how to calculate the Shemitah based on the number of years that have passed since the destruction of the second Beis ha'Mikdash. As Rashi explains, the basis for the Gemara's calculation is the Gemara in Ta'anis (29a) which says that the year in which the Beis ha'Mikdash was destroyed was the year after Shemitah (that is, the first year of a new Shemitah cycle).
In what year was the second Beis ha'Mikdash destroyed? The TUR (CM 67) writes that according to the calculation of RASHI here, the year 5087 (1327 C.E.) was a Shemitah year. Extrapolating backwards, this means that the Beis ha'Mikdash was destroyed in the year 3828 (68 C.E.), and the preceding year was a Shemitah year. This is consistent with the dating of the Churban given by the Gemara here (see Chart).
This calculation is not unanimous, however. The Tur writes that according to the RI (see TOSFOS here), the Shemitah year occurred in the year 5088 (1328 C.E.). According to this figure, the Churban occurred in the year 3829 (69 C.E.), and the previous year (3828) was a Shemitah year.
The RAMBAM (Hilchos Shemitah 10:6) cites the broadly accepted tradition of the Ge'onim, according to which the year 4935 (1175 C.E.) was a Shemitah year. This means that the year 5089 (1329 C.E.) was a Shemitah year. Extrapolating backwards, this means that the Beis ha'Mikdash was destroyed in the year 3830 (70 C.E.), and the preceding year was a Shemitah year. This opinion is consistent with the current system of counting the Shemitah cycle (the most recent Shemitah years were 5761 and 5768, or 2001 and 2008 C.E.).
Why do the opinions vary with regard to the year in which the Beis ha'Mikdash was destroyed? The Gemara says explicitly that the Beis ha'Mikdash was destroyed in the year 3828 (68 C.E.)!
Moreover, how could the Churban have occurred in the year following a Shemitah year? The Beis ha'Mikdash stood for 420 years (a number divisible by 7), and, according to Rebbi Yehudah (whose opinion is accepted by the Gemara here and by the Halachah), the Shemitah year occurs every seven years (even after a Yovel year). Accordingly, since the Shemitos were counted from the time that the Jews returned to the land and rebuilt the second Beis ha'Mikdash (because the Kedushah of the land was annulled when the first Beis ha'Mikdash was destroyed), the year in which the Beis ha'Mikdash was destroyed should have been a Shemitah year, and not the year after a Shemitah year.
(a) RASHI explains that the Churban occurred 3828 years after the creation of the world. In response to the second question, Rashi explains that the Shemitah count did not begin immediately when the second Beis ha'Mikdash was built. Ezra arrived only six years after the construction began, and he re-sanctified the land with regard to counting the years of Shemitah and with regard to the other laws that depend on the Kedushah of the land.
(b) TOSFOS and the RASHBAM answer the second question by explaining that the Beis ha'Mikdash was destroyed 421 years, and not 420 years, after it was built. Accordingly, the year in which the Beis ha'Mikdash was destroyed indeed was the year that followed Shemitah (since, as mentioned above, the Shemitah count began when the Jews returned to the land and rebuilt the Beis ha'Mikdash, and 420 is divisible by seven).
Tosfos and the Rosh reject this approach because it cannot be reconciled with the Beraisa's calculation (beginning of 9a). The Beraisa states that the second Beis ha'Mikdash stood for 420 years.
The DERISHAH (CM 67:9) explains that the Beraisa earlier counts only full years when it says that the Beis ha'Mikdash stood for 420 years. The Beis ha'Mikdash continued to stand, however, for a number of months after 420 full years passed from the time it was rebuilt. The calculation that Rav Papa provides for determining how many years have passed since the Churban considers the year that the Beis ha'Mikdash was destroyed as being the year after the Churban, since "one day out of a year is counted as a year" (Rosh Hashanah 2b). However, the calculation for determining the Shemitah year is based on the number of full years after the Churban (or 420 years).
Others, such as the BA'AL HA'ME'OR, do not have the words, "add one year," in the Gemara's calculation. Hence, the calculation of Shemitah may also be computed by counting the year in which the Churban occurred as year one after the Churban, because of the months that remained in the year in which the Churban occurred. Since that year was the first year of a Shemitah cycle, the seventh year of that cycle and every seventh year henceforth will be a Shemitah year.
The Ba'al ha'Me'or suggests further that the calculation of the Gemara here does not involve the number of years that have passed since the Churban, but rather it is based on the number of years from the creation of the world. Accordingly, the Girsa of "add one year" is correct: if -- when one adds one to the number of years since creation passed -- that number is divisible by seven, then that year is a Shemitah year. Consequently, year 420 of the Beis ha'Mikdash (or 3828 from creation) was a Shemitah year, since adding one to that year equals a sum (3829) that is divisible by seven.
RABEINU TAM also dates the Churban at year 421 after the Beis ha'Mikdash was rebuilt. He reconciles the calculation of the Gemara based on another variant Girsa.
The RAMBAM (Hilchos Shemitah v'Yovel 10:4) sets the date of the Churban at year 420, as Rashi does. However, he explains that the Gemara in Ta'anis does not mean that the year of the Churban was the year after Shemitah, but rather that the year that began two months after the Churban was a year after Shemitah.
According to all of these opinions, the year 3828 was a Shemitah year, in contrast to Rashi's opinion.
(c) If the Rambam agrees with the Ri who says that year 420 of the second Beis ha'Mikdash was a Shemitah year, then why does he calculate the Shemitah year as being 5089, one year later than the Shemitah year that the Ri calculates?