Ten Days of Repentance
The first ten days of the Jewish year (since the beginning of Rosh Hashanah until the end of Yom Kippur) are known as Ten Days of Repentance. During this period is "extremely appropriate" for Jews to practice Teshuvah (repentance, literally 'return'), which is to examine their own actions and repent of the errors committed against both God and neighbor, in anticipation of Yom Kippur. This repentance can take the form of additional petitions, confession of our own actions before God, fasting, and self-reflection. On the third day, Tzom Gedaliah.
Yom Kippur - Day of Atonement
Main article: Yom Kippur
* Erev Yom Kippur - Tishrei 9
* Yom Kippur (יום כיפור) - 10 Tishrei
Yom Kippur is considered by Jews as the holiest and most solemn day of the year. In it, is given special emphasis to forgiveness and reconciliation. Eating, drinking, bathing, anointing with oil, and close relationships are prohibited. Fasting begins at sundown, sun, and ends after nightfall the following day. The Yom Kippur services begin with the prayer known as Kol Nidrei, which must be recited before sunset sunset. Kol Nidrei, which in Aramaic means "all vows," is the cancellation of public religious vows made by Jews during the previous year. Concerns only unfulfilled vows made between a person and God, and not cancel or nullify any vows made between people.
A Tallit (prayer shawl with four points) is placed to the prayers of the night, the only evening of the year when this is done. The Ne'ila is a special religious service held only on Yom Kippur, and deals with the closing of the holiday. Yom Kippur ends with the blowing of the shofar, which marks the end of fasting. It is always observed as a fetividade one day only, both in Israel and the Jewish Diaspora community.
Source : http://pt.wikipedia.org/wiki/Festas_judaicas