Not everyone agrees with this, though. The Tur writes that according to the
RI (see TOSFOS here), Shemitah occurred in the year 5088 (1338 C.E.).
According to this date, the Churban occurred in the year 3829 (69 C.E.), and
the previous year (3828) was Shemitah.
Why are there varying opinions regarding 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!
In addition, how could the Churban have occurred in the year following a
Shemitah year? We know that the Beis ha'Mikdash stood for 420 years (a
number divisible by 7), and, according to Rebbi Yehudah (whose opinion is
accepted by our Gemara and by the Halachah), Shemitah 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 that the Beis ha'Mikdash
was destroyed should be 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. Regarding 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 building was begun, and he
re-sanctified the land with regard to counting the years of Shemitah and
with regard to the other laws dependant upon 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 after it was built. Since the year
420 was Shemitah, the year in which the Beis ha'Mikdash was destroyed indeed
was the year that followed Shemitah.
Tosfos and the Rosh reject this approach, because it cannot be reconciled
with the Beraisa's calculation (beginning of 9a), in which the Beraisa
states that the second Beis ha'Mikdash stood for 420 years.
The DERISHAH (CM 67:9) explains that the Beraisa earlier was counting only
*full* years, and it is saying that the Beis ha'Mikdash stood for 420 full
years. The Beis ha'Mikdash continued to stand, however, for a number of
months after 420 full years had passed since its rebuilding. 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 (i.e.
420 years).
Others, such as the BA'AL HA'ME'OR, do not have the words, "add one year,"
in the calculation of our Gemara. 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 our Gemara 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.
According to this, 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 our Gemara based on another
variant Girsa.
The RAMBAM (Hilchos Shemitah v'Yovel 10:4) sets the date of the Churban at
year 420, like Rashi. 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?
The MAHARLBACH (#142, section 5, cited by the DERISHAH CM 67:9) addresses
this question. He points out that there are two ways of counting the years
from the creation of the world. The years can be counted either from the day
that Adam ha'Rishon was created (which was Rosh Hashanah, according to Rebbi
Eliezer, whose opinion we follow; see Rosh Hashanah 12a and Insights there),
or from the year *before* Adam ha'Rishon was created, by adding an extra
year to the count. The reason an extra year is added is because the creation
of the world actually started five days before the creation of Adam
ha'Rishon, and we know that part of a year is considered a year ("one day
out of a year is counted as a year," Rosh Hashanah 2b). According to the
opinion of Rebbi Yehoshua, Adam ha'Rishon was created in Nisan, which was a
half a year before the first Rosh Hashanah, and thus there is even more of a
reason to add one year to the count of years, rather than to begin the count
at the first Rosh Hashanah. (For the purpose of calculating the Molad, it is
also convenient to include the extra year.) This extra year is referred to
as the "Shenas Tohu," the "year of nothingness," since the world -- for most
of that year -- had not yet been created. It is also referred to as the year
of "BaHaRaD," an acronym for the moment of the Molad of the Rosh Hashanah of
the year prior to creation (based on extrapolating backwards in time) had
the heavenly bodies been in existence at that time. ("BaHaRaD" stands for
"Monday" (day two, or "Beis"), five hours ("Heh"), and 204 Chalakim ("Reish"
and "Dalet") into the day.) The Molad for the following Rosh Hashanah (the
first Rosh Hashanah of the world) was "V-Y-D" (this stands for Friday (day
six, or "Vav"), at the end of the fourteenth hour ("Yud" and "Dalet") of the
day; see TOSFOS in Rosh Hashanah 8a, DH li'Sekufos).
Our count of years from creation (such as counting the current year as 5763)
includes the added year of "BaHaRaD." Does the Gemara's count of the years
until the Churban of the Beis ha'Mikdash include that additional year? The
Maharalbach asserts that it cannot include an extra year, since the Gemara's
calculation is based directly on the number of years that Adam ha'Rishon and
his descendants lived. Since Adam ha'Rishon was born on Rosh Hashanah of
"V-Y-D," there would be no reason to add an extra year to his age because of
the year of "BaHaRaD." The Maharalbach points out that this is alluded to in
the words of the Rambam (in Hilchos Shemitah v'Yovel 10:2), who contrasts
the year of the creation of Adam ha'Rishon to the year from which the
counting from creation begins. The Maharalbach proves that this is also the
opinion of RAV SA'ADYAH GA'ON and RAV HAI GA'ON.
Accordingly, the Shemitah year which occurred 3828 years from the creation
of Adam ha'Rishon actually occurred in the year 3829, according to our count
of years. Even though the Rambam accepts the opinion of the Ri, nevertheless
the correct date for the Shemitah year is 5089, and not 5088, because of the
added year.
Does the Ri disagree with the calculation of the Rambam? The Maharalbach and
the TASHBATZ (2:99) write that the Ri and the Rambam are in agreement. When
the Tur writes that according to the Ri, Shemitah was in 5088 and, according
to Rashi, it was in 5087, he is counting the number of years since the
creation of Adam ha'Rishon, just like the count of the Gemara with regard to
the Churban. (There indeed was a widely-held practice to count the year of
creation in that manner among the Jews of Oriental countries, as the
Maharalbach and the Ba'al ha'Me'or here mention. They would have counted the
current year as 5762 and not 5763.) Therefore, the correct year of Shemitah
according to our way of counting is 5089 according to the Ri, or 5088
according to Rashi. Consequently, the year given by the Ri is the same year
as that given by the Rambam.
The TESHUVOS KOL MEVASER (1:60) does not accept the view of the Maharalbach.
He asserts that according to Rashi and the Ri, the count of the Gemara which
puts the year of the Churban at 3828 *is already* including the year of
"BaHaRaD," since Adam ha'Rishon was created before the Molad of the Rosh
Hashanah after creation (of "V-Y-D"). Thus, there indeed are three opinions
regarding the correct calculation of the Shemitah year. According to Rashi,
Shemitah was in the year 5087, according to the Ri in 5088, and according to
the Rambam in 5089.