There are four new year days: On the first of Nissan is the new year for [reckoning the reigns of Jewish] kings and for [establishing the order of] the holidays.  On the first of Elul is the new year for the tithe of animals. R’ Elazar and R’ Shimon say: [It is] on the first of Tishrei.  The first of Tishrei is the new year for [reckoning] the years, for the Sabbatical years, for the Jubilee years, for the planting [of trees], and for the vegetables.  On the first of Shevat is the new year for the tree; according to the words of Beis Shammai. Beis Hillel say: On the fifteenth thereof.

At four junctures [of the year] the world is judged: on Pesach for the grain; on Shavuos for the fruit of the tree; on Rosh Hashanah all who walk the earth pass before Him like young sheep, as it is said: Who fashions all their hearts together, Who understands all their deeds; and on the Festival they are judged for the water.

For six months, the messengers go forth: for Nissan, because of Pesach; for Av, because of the Fast; for Elul, because of Rosh Hashanah; for Tishrei, because of the [proper] determination of the holidays; for Kislev, because of Chanukah; for Adar, because of Purim. And when the Temple was in existence, they went forth also for Iyar, because of [the] minor Pesach.

For two months, the witnesses may desecrate the Sabbath: for Nissan, and for Tishrei, for on them the messengers go forth to Syria, and on them they fix the holy days. And when the Temple was in existence, they desecrated even for all of them because of the determination [of the time] of the sacrifice.