Commentary for Avodah Zarah 17:11

Yose b. Rabbi counts how many years each kingship ruled. The Persians ruled for 34 years after the Temple was rebuilt. Greece than ruled 180, then Hasmoneans began to rule. They ruled 103 years and then Herod’s family ruled for 103 years. If we assume, as the sugya does, that the Roman rule began at the same time that the Greeks were expelled, then the Romans ruled 206 years, not 180!

This is how the sugya arrives at the calculation that Rome kept faith with Israel for 26 years and therefore, those years are not reckoned in the calculation of Rome’s dominance over Israel.

If a “Tanna” a reciter of texts, forgets exactly how many years it has been since the Destruction of the Temple, he can ask a notary and then just add twenty. This is because notaries follow the secular dating which began 380 years before the destruction, when the Greeks began to rule. So for instance, if it’s 452 according to the secular dating, then it is 72 after the destruction of the Temple.

Vice versa holds true for the notary.
What is interesting in this sugya is the existence of two separate ways of counting years—a secular one and a religious one. Such a phenomenon continues to this day, although we use two altogether different systems, a Christian one and one that counts from the creation of the world.

The Messiah was supposed to come 2000 years after the Israelites accepted the Torah, which was given 2000 years after creation. But due to the sins of humanity (or the sins of Israel) the Messianic age has not yet arrived.
Another interesting note on this source is that without Torah, the world was chaos. Perhaps this is the Talmud’s way of noting that without the ordering laws of the Torah, there would be chaos in the world.

When do we start counting the two thousand years of Torah? If you start counting at the actual giving of the Torah on Sinai, it was not 2000 years. If you start counting at creation, there are more than 2000 years before the Torah was given. The Torah was given at year 2448 from creation, and therefore the time of the Messiah will begin before the 2000 years of Torah end, assuming the world will last only 6000 years.

As stated above, if we count the time from the giving of the Torah, we are 448 years short for the 2000 years of Torah. Therefore, we start with the date at which Abraham and Sarah began to “make souls in Haran.” According to midrash, this refers to their converting the local population to monotheism. Abraham was 52 years old when he began doing this. If he was born exactly 500 years before the Torah was given, then from the date he began proselytizing until the intended arrival of the messianic age there are 448 years!
I think there is also something meaningful in the notion that “Torah” begins not with the “Torah” but with human beings reaching out to other human beings to teach them.

If the tanna remembers how many hundreds of years have passed into the years of the Messiah, meaning the third period of 2000 years, but does not remember the exact number of years, he can ask a scribe who counts by the secular years and add 48. So for instance if it is the year 325 in the secular years then it must be the 73rd year of the Messianic cycle, plus whatever hundred they happen to be in.