[San 11b: We begin at the two dots 19 lines from the top of the page.]
The rabbis taught in a b'raita: We intercalate the year [i.e., extend the year by adding a month] because of Aviv, the fruits of the trees, and the season.
[The Torah {Ex 13:4 and Deut 16:1} specifies that Pesach must be in the Aviv. In modern Hebrew, this means spring, but the etymology of the word is the ripening of the grain. Thus, Pesach must coincide with the time of year in which the grain ripens.]
[The fruits of the trees refers to the obligation to bring the first fruits to the Temple {Ex 23;19: Deut 26:2}. It was convenient to bring them at Shavuot, when the farmers were going to Jerusalem for their pilgrimage anyway. Thus, if the fruits were not to ripen before Shavuot, the year would be extended to allow additional time for ripening.]
[In rabbinic astronomy, the seasons were marked by when the sun first crosses the equator {the spring and fall equinoxes} and when the sun reaches it's maximum distance from the equator {the winter and summer solstices}. The lunar calendar had to remain synchronized with these astronomically defined seasons; if the asynchrony was sufficient, a leap year would be declared.]
We intercalate for any two of these, but not for only one. And when Aviv was one of these [reasons], everyone was happy. [Rashi: New grain could not be eaten until after the second day of Pesach, so extending the year meant that the people had to wait an extra month before eating the grain of the current harvest. If the grain was not yet ripe, the people were not displeased by the extension of the year. However, if the grain was ripe in time but could still not be eaten, because the year had been extended for other reasons, the people were unhappy, ]
Rabban Shimon b. Gamliel said: Because of the season.
They [the rabbis] asked: Does (R. Shimon) mean that they are happy when the year is intercalated because of the season [as one of the two reasons] , or (is it his opinion) that we intercalate because of the season [even if there is no other reason to do so]?
The issue stands [unresolved].
The rabbis taught in a b'raita: We intercalate the year for [crop ripening] in three areas [of Israel]: Judea, Trans-Jordan, and the Galilee. We intercalate for (any) two of them, but not for only one of them. And when Judea was one of them, everyone was happy, because the Omer is brought only from Judea.
[The Omer offering was brought on the second day of Pesach. Ideally, the barely used for the Omer offering should be fresh and newly-ripened. If the year was extended because of late crops in Trans-Jordan or the Galilee, the Omer from Judea would no longer be as fresh, and the people would be disappointed. But if a leap year was declared because the Judean barley was late in ripening, the people would be happy; their Omer offering would be fresh and newly-ripened.]
The rabbis taught in a b'raita: We do not intercalate the year except in Judea. But if it was intercalated in the Galilee, it is intercalated. Hananiah of Ono testified: If it was intercalated in the Galilee, it was not intercalated. R. Yehudah b. R. Shimon b. Pazi said: What is the reason for Hananiah of Ono's ruling? The Torah says (Deut 12:5): "Even unto His habitation ye shall seek and thither shalt thou come" -- any "seeking" can only be in the place of God's Dwelling [i.e., Judea].
The rabbis taught in a b'raita: We do not intercalate the year except during the day, and if they intercalated at night, it is not intercalated. And we do not intercalate the month except during the day, and if they intercalated at night, it is not intercalated.
R. Abba said: From what verse (can this be derived)? From [Ps. 81:4] "Blow the horn at the New Moon, at the full moon of our feast day". On which feast day is the moon hidden? [The word used for New Moon is "keseh", which is etymologically related to "kaseh" - to hide.] It must be Rosh haShanah. [All the other holidays fall near the middle of the month, when the moon is visible; only Rosh haShanah falls at the beginning of the month, when the moon is not visible.]
[Having established that the verse refers to Rosh haHanah, the gemara continues with its analysis:]
And it is written [in the following verse] "For it is a statute for Israel, and ordinance ["mishpat"] for the God of Jacob." Just as "mishpat" [judgment] must be rendered during the day, so must sanctification of the New Moon be done by day. [The rule that judgment can only take place during the day is based on exegesis of the biblical verse on inheritance, and is discussed on Sanhedrin 34b.]
[We end on the last line of San 11b.]