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.