But what exactly is Rosh Hashanah and how is it celebrated? Yom Kippur comes on the last of the 10 days of repentance that began with Rosh Hashanah. This year in 2025, Rosh Hashanah begins at sunset on Monday, Sept. 22, and ends at sunset on Wednesday, Sept. 24. How is Rosh Hashanah celebrated? Rosh Hashanah observances include special foods, traditions and mitzvahs, or commandments, and celebrations can vary from family to family.