The Jewish New Year
The Days of Awe begin with Rosh Hashanah (“head of the year”), a holiday commonly known as the Jewish New Year. Rosh Hashanah is a joyous day, perhaps because it commemorates the creation of the world. Most Reform Jews and Jews living in Israel celebrate Rosh Hashanah for one day; other Jews in the Diaspora observe Rosh Hashanah (and many other one-day holidays) for two days, a practice that acknowledges their distance from Israel and their inability to celebrate the holiday during the proper times (because of time difference).
The Jewish calendar contains three other “new year” celebrations: the first day of Nisan, the springtime month of Passover, which begins the counting of the calendar months and the reign of kings; the first day of Elul, the month preceding Rosh Hashanah, because it's the symbolic new year for tithing animals, a form of charity; and Tu B'Shevat, the fifteenth day of Shevat, which marks the new year for trees.
Origins of the Holiday
The Torah contains two distinct commandments to observe Rosh Hashanah. In Leviticus 23:24–25, it is written that on the first day of the seventh month, there “shall be a solemn rest unto you, a memorial proclaimed with the blast of horns, a holy convocation.” Later, in Numbers 29:1, it is proclaimed that this day shall be a “holy day,” a day when Jews should not work, and a day when “the shofar is trumpeted.”
In fact, the Torah only refers to Rosh Hashanah as Yom Teruah (the day of the sounding of the shofar) or Yom Ha-Zikaron (the day of remembrance). The latter term is a reference to Abraham's willingness to sacrifice his son Isaac in demonstration of his unswerving obedience to God, which is said to have occurred on the first of Tishri.
One explanation for avoiding the term Rosh Hashanah (head of the year) may have had to do with similar New Year celebrations and moon festivals practiced by pagans around the same time, in the early fall. The term Rosh Hashanah emerged much later, sometime during the Talmudic period (the first five centuries of the Common Era). However, we know that the holiday itself was well established by the fourth century B.C.E., when some of the Jews had returned from the Babylonian exile to construct the Second Temple in Jerusalem.