Study Rosh Hashanah folio 20B with parallel Hebrew-English text, traditional commentary, and modern study tools. Free access to Babylonian Talmud online.
In this case, where the witnesses withhold testimony about what they saw and the New Moon is pushed off to the next day, it looks like a lie, as the moon might have been seen by others as well, and people will wonder why the New Moon was not sanctified the previous day. In that case, where the witn
§ Shmuel said: I am able to fix the calendar for the entire Diaspora without witnesses. Shmuel was an expert on the movement of the celestial bodies and on the principles governing leap years and additional days added to months.
Abba, the father of R' Simlai, said to Shmuel: Does the Master know the meaning of this statement, as it is taught in a baraita dealing with the secret of addition, which discusses calendric calculations: Differentiate between when the molad occurred before midday and when the molad occurred after
As for the meaning of this obscure baraita, when R' Zeira went up from Babylonia to Eretz Yisrael, he sent back a letter to his colleagues in Babylonia: In order for a day to be sanctified as the New Moon, it is necessary that both the night and the day be of the new month. That is to say, the molad
And this is what Abba, the father of R' Simlai, said: The baraita means as follows: They calculate the molad; if the molad occurred before midday, so that there are at least 6 more hours left of the day, it is known that the moon will be visible close to sunset. If, however, the molad did not oc