Rabbi Yosei says: The year must be intercalated only if twenty-one days of Tishrei will pass before the autumnal equinox. The Gemara explains: And both of them expounded the same verse to arrive at their respective opinions: “And the Festival of the Ingathering at the turn of the year” (Exodus 34:22). They both interpret the verse to mean that the Festival of the Ingathering, which is referring to the intermediate days of Sukkot, must take place during the season of Tishrei, i.e., autumn. One Sage, Rabbi Yehuda, holds that we require all of the Festival to take place in the new season, after the equinox. And one Sage, Rabbi Yosei, holds that we require only some of the Festival, even one day, to take place in the new season, so the year must be intercalated only if the equinox would fall on the twenty-second of Tishrei or later.

The Gemara asks: What do they each hold? If they hold that the day of the equinox concludes the season, meaning that it is counted as part of the preceding season, then even if the season of Tammuz is not lacking more than this number of days until its completion, the year would need to be intercalated. According to the one who says that we require all of the Festival to take place in the new season, this is not sufficient to rectify the problem, as the sixteenth of Tishrei, which is the beginning of the Festival of the Ingathering, is still in the old season. And even according to the one who says we require only some of the Festival to take place in the new season, this is also not sufficient to rectify the problem, since if the equinox occurs on the twenty-first of Tishrei, the new season begins only on the twenty-second, after the Festival of the Ingathering is over. Rather, they certainly both hold that the day of the equinox begins the new season.

The Gemara raises an objection to this conclusion from a different baraita: The day of the equinox concludes the season; this is the statement of Rabbi Yehuda. Rabbi Yosei says: The day of the equinox begins the season. It is therefore clear that they disagree about this issue, and that the previous baraita must be explained differently.

And furthermore, it is taught in a baraita (Tosefta 2:7): The court intercalates the year only if the season of Tammuz was lacking its completion for most of the month of Tishrei. And how much is: Most of the month? Sixteen days. Rabbi Yehuda says: Two parts, meaning two-thirds, of the month. And how much is: Two parts of the month? Twenty days, since in that case the day of the equinox would fall on the twenty-first, and since according to Rabbi Yehuda the day of the equinox concludes the season, the new season would begin on the following day, after the Festival of the Ingathering has ended.

The baraita continues: Rabbi Yosei says: The court calculates the seasons, and if the winter season of Tevet, which is before Passover, is lacking its completion for sixteen days into the month of Nisan, the court intercalates the year, so that Passover will occur within the season of Nisan, i.e., the spring. But if the summer season of Tammuz, which is before the Festival of the Ingathering, is lacking its completion for sixteen days into the month of Tishrei, the court does not intercalate it. Rabbi Shimon says: Even if the season before the Festival of the Ingathering is lacking its completion for sixteen days into the month of Tishrei, the court does intercalate the year. The tanna referred to as Aḥerim says: The year is intercalated even on account of a minority of the month, and how much is a minority of the month? Fourteen days. The Gemara concludes: Comparing the various baraitot poses a difficulty, as they appear to contradict one another.

The Gemara analyzes the baraita: The Master said that Rabbi Yehuda says: The year must be intercalated if the season of Tammuz is lacking its completion for two parts of the month of Tishrei, which is twenty days. Rabbi Yosei says: The court calculates the seasons, and if the season of Tevet, which is before Passover, is lacking its completion for sixteen days into the month of Nisan, the court intercalates the year. The Gemara challenges: That is the same as the opinion of Rabbi Yehuda, since a calculation that shows the winter season of a given year to be lacking its completion for sixteen days of Nisan will also show the summer season of that year will be lacking its completion for twenty days of Tishrei.

The Gemara explains: The difference between them concerns the question of whether the day of the equinox concludes the season, or the day of the equinox begins the season. Rabbi Yehuda holds that the day of the equinox concludes the season, and therefore in the given scenario the year must be intercalated so that some of the Festival of the Ingathering will occur in the season of Tishrei. But according to Rabbi Yosei this is not a concern, as the day of the equinox begins the season. Nevertheless, the year must be intercalated so that Passover will occur in the season of Nisan.

The Master says: In the continuation of his statement, Rabbi Yosei said: If the summer season of Tammuz, which is before the Festival of the Ingathering, is lacking its completion for sixteen days into the month of Tishrei, the court does not intercalate the year. The Gemara challenges: Rather, according to Rabbi Yosei, if the season before the Festival is lacking its completion for sixteen days into the month of Tishrei, this is the situation when the court does not intercalate the year. But can one therefore infer that if it is lacking its completion for seventeen or eighteen days into the month of Tishrei, the court does intercalate the year?

The Gemara explains the difficulty: But doesn’t he say: The court calculates the seasons, and if the winter season of Tevet, which is before Passover, is lacking its completion for sixteen days into the month of Nisan, yes, the court intercalates the year; but if it is lacking its completion for less than that, it should not be intercalated, even if the season before the Festival of the Ingathering will be lacking seventeen or eighteen days? The two elements of Rabbi Yosei’s statement appear to contradict one another.

The Gemara answers: No, those inferences are not correct. Rather, in both this case and that case, the court does not intercalate the year, and since it taught in the first clause: Sixteen days before Passover, it also taught: Sixteen days before the Festival of the Ingathering, but one cannot infer from this that it means sixteen days and no more.

The baraita teaches that Rabbi Shimon says: Even if the season before the Festival of the Ingathering is lacking its completion for sixteen days into the month of Tishrei, the court does intercalate the year. The Gemara asks: If so, this is apparently the same as the opinion of the first tanna; what is the difference between Rabbi Shimon’s opinion and that of the first tanna?