The first day of the month of Tishrei is described as a day of "memorial proclaimed with the blast of the horns" and as "a day of blowing the horn." The Mishnah lists four days during the year which it describes as Rosh Hashanah, the Head of the Year: The first of Nissan is the New Year for the Jewish kings and for the religious calendar; the first of Elul is the New Year for tithing cattle; the fifteenth (TU) of Shevat is the New Year for trees; and the first of Tishrei is the New Year for the civil calendar, for the Shmita (Sabbatical) and Yovel (Jubilee) years. On this last day, according to the Mishnah, "the whole world is judged."

These motives dominate the period which starts with Rosh Hashanah and ends with Yom Kippur. Rabbinic theology sees these days as the time when man's fate is fixed on high. In the words of a famous Talmudic homily: Three books are opened on Rosh Hashanah, one for the completely righteous, one for the completely wicked, and one for the average person. The completely righteous are immediately inscribed in the Book of Life, the completely wicked are immediately inscribed in the Book of Death. The average person is kept in suspension from Rosh Hashanah to the Day of Atonement. If he deserves well, he is inscribed in the Book of Life, if not in the Book of Death.

Since the overwhelming majority of people are neither saints nor beyond redemption, the Ten Days of Repentance should be used for an intensive spiritual effort to better one's lot. A concomitant of this theology is the doctrine of repentance, T'shuva, which teaches that if a man repents his sins, they will be forgiven. Several changes are made in the liturgy for these special ten days. We say Holy King, the Just King; we add "Remember us for life, inscribe us in the Book of Life" and in the last benediction of the Amida, "May we and all Thy people Israel be remembered and inscribed before Thee in the Book of blessing, peace and prosperity for a good life and for peace."