Michael Lewyn writes:
You write [ in Avot 054 – SR] that Hillel became famous for ascertaining whether the Paschal lamb could be sacrificed on a Shabbat that overlapped with Pesach. But Jews had been celebrating Pesach for 1200 or so years before Hillel was born – so why hadn't this problem been solved in the intervening centuries?
I respond:
First of all let me suggest a slight correction. I do this not because I am being pedantic (which sometimes I can be!) but because I am concerned that people reading this shiur might misunderstand. Michael describes a situation in which "Shabbat overlapped with Pesaĥ". But, of course, this happens every year: since there are seven days in Pesaĥ one of them, every year, must be Shabbat! The problem that Hillel and his contemporaries were facing was not Shabbat and Pesaĥ "overlapping"; the problem was that the day before Pesaĥ fell on a Shabbat – in other words, the first day of Pesaĥ was on a Sunday.
Having made that corrective suggestion, let me try to relate to Michael's main point. First of all, as I pointed out in the original shiur, this calendrical problem does not occur all that often. This seems to have been the case ever since the Jewish people adopted the permanent calendar in the 4th century CE. We cannot know for sure what the situation was before then when the calendar was essentially regulated by actual observation of the phases of the moon. However, we may be permitted to suspect that the body that regulated the calendar – the Sanhedrin – permitted itself to manipulate the data for ulterior purposes, both to the general benefit of all Israel and to someone's personal benefit. For example, we have knowledge that when the question arose whether to declare a certain year to be a leap year or not (with an extra month intercalated) it was decided [Sanhedrin 18b] not to let the High Priest take part in the discussion. This was because previous experience had taught that High Priests, who probably were rather advanced in years, would always vote against intercalation because they would prefer to strip and bathe in cold water five times during Yom Kippur during the month of September rather than October. There was possibly a similar manipulation concerning Rosh Ĥodesh Nisan in order to prevent the 14th of the month from falling on Shabbat, with all its attendant difficulties.
However, of course, this could not be done ad infinitum. And let us note very carefully that Hillel did not invent the solution: he freely admits in the end that he now recalled that this was what he had learned from his teachers, so the problem had been dealt with previously.
