Before we answer the question above, let’s lay the groundwork. In Leviticus 23, God revealed details of His “appointed times,” also known as the 7 major Jewish feasts. Three were to be commemorated in short order in the spring. (Feasts of Passover, Unleavened Bread and First Fruits) The fourth was Penecost. Then, three fall feasts followed several months later. (Feasts of Trumpets, Yom Kippur and Tabernacles)
We are in the midst of those fall feasts right now! The Feasts of Trumpets commenced last Friday at sundown.
But, in Jewish culture today, that feast day is widely known as Rosh Hashanah, “Head of the Year.” Jews celebrate that day as their New Year’s Day, though Leviticus 23 seems to clearly identify the new year beginning with the first feast (Passover).
So, what changed and how? One for Israel explains: How the Feast of Trumpets Became Rosh HaShana