The Mishnah (rh 1:1) enumerates four separate days of the year, each of which is regarded as a New Year (Heb. *Rosh Ha-Shanah, lit. "head of the year"). The fixing of those dates was essential, not only for civil and political purposes, but for the regulations concerning the procedure regarding the religious injunctions connected with agricultural produce. Since, for example, the tithe had to be given of animal produce, the fruit from the first three years of a tree's growth (*orlah) was forbidden, and the beginning and end of the *Sabbatical year had to be determined, it was necessary to lay down when the year began for those various calculations. With one exception (and that only according to *Bet Hillel), all the New Years begin on the first of the month.
(1) The first of Nisan is the New Year for (Jewish) kings and for the religious calendar (for festivals). Thus if a king ascended the throne during Adar, the next month would constitute the second year of his reign, and Passover is the first festival of the year. The Talmud (rh 7a) adds that it is also the New Year for the purchase of congregational sacrifices with the *shekalim collected in Adar, and for the renting of houses.
(2) The first of Elul is the New Year for the tithing of cattle (but see the first of Tishri), i.e., tithes had to be given for all cattle born between the first of Elul and the 30th of Av.
(3) The first of Tishri is the New Year for the civil calendar (including the counting of the reigns of foreign kings; see rh 3a–b and cf. Git. 8:5) for the Sabbatical and Jubilee years (plowing and planting being forbidden from that date), and for the year of planting of fruit and vegetables. The establishment of the first of Tishri as the religious New Year (see *Rosh Ha-Shanah) depends upon the statement that on that day "all the world is judged" (rh 1:2). According to R. Simeon and R. Eleazar the first of Tishri is also the New Year for the tithing of cattle and therefore there are only three New Years.
(4) The first of Shevat is the New Year for trees, according to Bet Shammai, but Bet Hillel fixed the date as the 15th of Shevat, and since the halakhah is established accordingly, it is this date which is celebrated today (see *Tu bi-Shevat). The reason given in the Talmud (rh 14a) is that on that date the greater part of the year's rain has fallen.
Only Rosh Ha-Shanah is fully celebrated, though in recent times a minor celebration has developed, especially in Israel, for Tu bi-Shevat. The others, as stated, are merely for calendrical computations.