In the Talmud, Rosh HaShana 8a, Rav Nachman bar Yitzchak said: The first of Tishrei is the New Year for judgment as it says in Dvarim 11:12 “The eyes of God are on it (the Land of Israel) from the beginning of the year until the end of the year.” This means that from the beginning of the year judgment is issued regarding what will occur at its end.
The Gemara explains how we know that the “beginning of the year” mentioned here refers to Tishrei. The answer is in Tehilim 81:4 “Blow a shofar at the moon’s renewal, when the moon is covered on our festive day.” Rosh HaShana is the festival when the moon is covered, since it falls at the beginning of the lunar month when the moon is hidden from view. The following verse (Tehillim 81:5) adds “Because it is a statute for Israel, a judgment day unto the God of Yaakov.” Therefore we see that Rosh HaShana (the first of Tishrei) is the day of judgment.
Why are we even questioning when the beginning of the year is? Isn’t it obvious that the New Year begins in Tishrei?
Actually, the first mishna in Rosh HaShana teaches us that there are four New Years: The first of Nisan is the New Year for the kings and the festivals. The first of Elul is the New Year for ma’aser (tithing) of animals (Rabbi Elazar and Rabbi Shimon say that the New Year for ma’aser for the animals is on the first of Tishrei). On the first of Tishrei is the New Year for reckoning the years and for Shmita (Sabbatical produce) and Yovel (Jubilee), for the sapling and for the vegetables. On the first of Shvat is the New Year for the tree, according to Beit Shammai. According to Beit Hillel it is on the fifteenth of Shvat.
We see from here that each New Year served a different purpose. Aside from the New Year in Tishrei being the day of judgment, it is also the date where we change the calendar year (5780- here we come!) as well as an important day for agriculture. In the Land of Israel, in a Shmita year, when one is forbidden to plant and work the land, that one day really makes a difference. The concept of Orla teaches us that we may not eat the fruits of the sapling for the first three years. If a sapling was planted in Elul, by Tishrei it would count as if the tree already existed for one year, even though it only technically existed for one month.
May we be judged favorably on Rosh HaShana in Tishrei, the day of judgment and may we merit to celebrate all four New Years in good health.