“In the seventh month.” The first day of the month Tishri was considered the first day of the year for over 2,500 years, from Adam until the Exodus. At the Exodus, God changed the Jewish calendar and switched it by six months. The seventh month, which had been Nisan (also called Abib), became the first month (Exod. 12:2). That change made the first month (Tishri) become the seventh month (see commentary on Exodus 12:2). The Hebrew “Rosh Hashanah” literally means “head of the year (from the Hebrew rosh, “head”).” This feast occurred on Tishri 1, the beginning of the civil new year (Lev. 23:24-25; Num. 29:1-6). The religious new year began on Nisan 1. Rosh Hashanah was to be a special day of rest and memorialized by blowing shofars, the ram’s horn trumpet, so it became known as the “Feast of Trumpets,” although that name is not in the Bible.
“a memorial.” Some scholars say the shofar blasts and sabbath is so God will remember the people and look favorably upon them, while others say it is for the people to remember God. It is likely for both: the people remember God, and He looks favorably upon their obedience to Him.
“shofar.” The ram’s horn trumpet, not the metal trumpet.