Ashkenazi Jews began reciting the Selichot prayers on Saturday night – the prayers asking G-d for forgiveness – a ritual that will be performed each night for the next week, until Yom Kippur, the Day of Atonement.
Sephardic Jews began doing this nearly a month ago, at the beginning of the Hebrew month of Elul. Many Jews also have the custom of blowing the shofar each day in the month of Elul as well, to awaken Jews to the importance of repentance.
It is believed that during this period, Moses ascended to Heaven and asked for mercy for the People of Israel – and 40 days later, on the Day of Atonement, his request was accepted.
There are only four days during the 10-day period of repentance (the period which falls between Rosh HaShanah and Yom Kippur) in which one does not recite the Selichot prayer service. These are the two days of Rosh HaShanah, the Sabbath that falls in between (Shabbat Teshuva), and Yom Kippur.
The traditional time to recite the Selichot prayer service is from midnight until the morning hours. However, another tradition is to awaken especially early, and to say the Selichot prayers prior to the regular Shacharit, or morning prayer service.
This year, Rosh HaShanah begins Wednesday evening at sunset, creating a three-day holiday, with the two days of the holiday on Thursday and Friday, and continuing into the Sabbath on Friday night and Saturday.