Another teaching of Rabbi Akiva: He will talk about five different situations where the judgment would be 12 months. Rabbi Akiva also used to say: There are five different things that have a duration of 12 months. The amount of time for the generation of the flood—from the start of the flood until everything dried up—was 12 months. Iyov was judged for 12 months. The judgment of the Egyptians, from the first plague all the way through the exodus, when Bnei Yisrael (the Jewish people) left Egypt, lasted 12 months. The punishment that Gog and Magog (a place) will receive in the end of days will last 12 months.
In the Yemot HaMashiach (in the end of days), Gog—who's the name of the Melech, the king of a place, Magog—will lead all the different nations of the world against the Jewish people in a war. And by the end, they will be gone. And that destruction, at the end of times, will last 12 months until they're wiped out. The amount of time that the wicked spend in Gehinam (hell) is also 12 months. As the Pasuk (verse) in Yeshaya says, “it will be from a month to its month.” We learn from here that a sinner is judged in Gehinam from the month to its month: the month he passes away, all the way to that month in the following year, which is a period of 12 months. This is where we get the custom to say Kaddish for someone who passed away, not for a full 12 months. We stop a little bit earlier. There are different customs out there. Some people will stop for a week after the 11th month is done and then resume for another three weeks, just to give off the impression that a person is not totally, totally wicked and would not need the full 12 months in Gehinam.
Rabbi Yochanan ben Nuri says that the judgment in Gehinam could be even as short as 49 days. 49 days is the time between Pesach and Shavuot. He learns that from the Pasuk at the end, continuing in Yeshaya, which says, “a Shabbat to its Shabbat.” We learn from here that Shabbat could also mean the time between Pesach and Shavuot. So we say that it could be referring to the time of the Omer (49 day period) between Pesach and Shavuot, and that a person's time in Gehinam could be that short. But Rabbi Yochanan ben Nuri would agree that if there's a really wicked person, that person would be in Gehinam for the full 12 months, like Rabbi Akiva told us.