Avodah Zarah Daf 9 עבודה זרח דַף 9

A Baraisa listed the various nations who ruled Eretz Yisroel during the second Beis Hamikdash, concluding that one can calculate dates based on how many years passed since the Churban. Rav Pappa says that if a Tanna teaching this Baraisa is unsure precisely how many years passed since the Churban (but presumably knows how many centuries passed), he should ask a scribe how many years he writes in his שטרות, which are dated from the Greek era, and add twenty years, thereby arriving at the correct number. Since the Greek era began 380 years before the Churban, adding twenty years completes the hundreds. If a scribe does not know which year to write in a שטר, he can ask a Tanna how many years he is counting from the Churban, and subtract twenty. The siman to remember who adds years and who subtracts years is: ספרא בצירא תנא תוספאה – a scribe subtracts; a Tanna adds. [A scribe writes words of the Torah with fewer letters, e.g., "משה" without a "ו", in accordance with the מסורה. A Tanna teaches "תוספתא", which literally means “addition.”]

The Yeshivah of Eliyahu taught: ששת אלפים שנה הוי העולם – the world will exist for six thousand years: the first two thousand years were תוהו – nothingness (i.e., devoid of Torah), the second two thousand were "תורה" (without Moshiach), and the final two thousand were destined to be ימות המשיח, but בעונותינו שרבו – because of our many sins, יצאו מהן מה שיצאו מהן – those [years] which have elapsed [from ימות המשיח] have already elapsed (and Moshiach has not yet arrived). The Gemara asks when the two thousand years of "תורה" begin, because מתן תורה at סיני can be proven to have occurred after the third millennium began (in the year 2448)!?

The Gemara answers that they are counted from the time of the passuk: "ואת הנפש אשר עשו בחרן" – and the people they made in Charan, when Avraham and Sarah first taught Torah to people and converted them. We have a tradition that Avraham was fifty-two years old at the time, completing two thousand years from Creation (Avraham was born in the year 1948).

Rav Pappa says that a Tanna trying to calculate how many years have been lost from ימות המשיח can add forty-eight years to a scribe’s date, and a scribe who does not know the year can ask a Tanna counting from ימות המשיח and add fifty-two years.

Rav Huna brei d’Rav Yehoshua said that one who does not know which year of the shemittah cycle he is in, may calculate it based on the Churban: The Churban occurred in the first year after shemittah, at the end of the year (Av), so that year is calculated as part of the Beis Hamikdash era. Therefore, he should first add one year. Then, he should divide the centuries into periods of Yovel, and add two years for each century, because a Yovel-cycle is forty-nine years (this follows the opinion of Rebbe Yehudah, whereas the Rabbonon hold a Yovel-cycle is fifty years). He then divides the פרטי – specific number (of the last two digits) by seven, and the remainder will represent the current year of the shemittah cycle. The siman to remember to add two years for each century is the passuk: כי זה שנתים הרעב בקרב הארץ – for these two years of famine throughout the land.