Рош Ха-Шана
The day before Rosh Hashanah day is known as "Erev Rosh Hashanah" ("Rosh Hashanah eve"). It is the 29th day of the Hebrew month of Elul, ending at sundown, when Rosh Hashanah commences. Some communities perform Hatarat nedarim (a nullification of vows) after the morning prayer services. Many Orthodox men immerse in a mikveh in honor of the coming day.