<html><P>R. Micha Berger wrote: <BR><BR><So I would think we now have two shitos:<BR><BR>R' Chananeil / R' Bachayei: we used an algorithm from day 1, this being<BR> the essence of the mitzvah<BR>Rambam: Until Abayei veRava, which could be as late as Hillel Nesi'ah,<BR> if they set the calendar up toward the beginning of his nesi'us.<BR> However, the Rambam might have held that Rav Ashi veRavina closed<BR> the Sanhedrin, not R' Gamliel IV.><BR><BR> Where does Rabbeinu Chananel say that an algorithm was used? All he says is that the cheshbon was used, and cheshbon and algorithm are not one and the same. AIUI, Moshe was told miSinai that the average time between molados is 29 days, 12 hours and 793 chalakim; that we begin calculations from an original molad of BHR"D, that the molad is unseen for six hours, and thus the time of the molad could be determined without recourse to eidim. But just as when r'iyah was used, the Beis Din was not required to act on the testimony they heard, but could refrain from being m'kadeish, so too could they refrain from declaring as Rosh Chodesh the day which came out al pi cheshbon, as indeed happens now. </P>
<P> The algorithm, on the other hand, did not come until the fixed calendar, and it consisted of more than just the use of the cheshbon for determining the molad: it fixed which months were to have 29 days and which 30, and which years should be m'ubaros, which were not part of the halacha-l'Moshe-'miSinai cheshbon. Where do you see anything in R. Chananel that says differently?</P>
<P> On a related matter, Tosafos in P'sachim 58b, d.h. K'ilu, says that Lo AD"U Rosh (or, rather, Lo D"U -- he says nothing about Sunday) was practiced during the time of kiddush al pi r'iya. This does not imply that Lo BD"U Pesach was in effect, since it is not an independent rule, but a consequence of Lo AD"U Rosh and the fixed number of days we now have between Pesach and Rosh Hashana. Today, if Pesach would be Monday, then RH would perforc be Wednesday. When r'iyah was used, a Monday Pesach did not automatically result in a Wednesday Rosh Hashana, since, e.g., Tammuz could have had 30 days, causing RH to be Thursday, or Av could have had 29, so that RH would be Tuesday. . </P>
<P> As for Rabban Gamliel's Yom Kippur, as R. Zev Sero pointed out, it wasn't an attempt to manipulate the calendar. Witnesses came on the thirtieth, and he was m'kadesh the new month (otherwise, the old one would automatically have been a thirty-day month). Then, when the moon was not visible that night, R. Yehoshua contended that it proved that the witnesses must have been wrong, and he therefore held that the month should indeed have been thirty days and Rosh Chodesh should be on the thirty-first. However, he was informed by R.Akiva that whether R. Gamliel's kiddush was based on true or false witnesses, what was done was valid and could not be undone because "atem afilu muta'in."</P>
<P>EMT</P></html>
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