The term “Rosh Hashanah” does not appear in the Torah, but is used in the Hebrew Bible in Ezekiel 40:1 in general reference to the “beginning of the year.”[6] Leviticus 23:24 refers to the festival of the first day of the seventh month as “Zicaron Terua” (“a memorial with the blowing of horns”).
Numbers 29:1 calls the festival Yom Terua, (“Day of blowing the horn”) and defines the nature of animal sacrifices that were to be performed.[6][7]
The Hebrew Bible defines Rosh Hashanah as a one-day observance, and since days in the Hebrew calendar begin at sundown, the beginning of Rosh Hashanah is at sundown at the end of 29 Elul.
The rules of the Hebrew calendar are designed such that the first day of Rosh Hashanah will never occur on the first, fourth, or sixth days of the Jewish week[8] (ie Sunday, Wednesday or Friday)