The Torah sets apart the first day of the seventh month as a sacred occasion marked by trumpet blasts and cessation from ordinary work. It later became known as Rosh Hashanah, the Jewish New Year.
For the first-century setting, it is safest to begin with the biblical festival and distinguish it from customs and meanings that became more fully developed later.
Leviticus 23 and Numbers 29 command a sacred assembly and trumpet observance on the first day of the seventh month. This month also contained the Day of Atonement and Tabernacles.
Ordinary work was interrupted by the sacred day. Worshipers heard or participated in the trumpet observance and entered a month containing several important religious occasions.
Trumpets and horns are known from ancient material and artistic evidence, although connecting a particular archaeological object directly with this festival is usually difficult.
Leviticus 23:23–25 and Numbers 29:1–6 provide the principal biblical descriptions. Later Jewish literature greatly expands the theological meaning and practices associated with the day.
The day belonged to the sacred seventh month and was marked by trumpet blasts, rest, assembly, and offerings.
The Gospels do not identify a particular event in Jesus' ministry with this festival.
The first day of the seventh month was an established biblical sacred day involving trumpet blasts and rest from ordinary work.
Later Rosh Hashanah customs and theological themes should not all be assumed to have existed in their later form during the ministry of Jesus.
The festival reminds us that the first-century Jewish calendar contained sacred occasions beyond those most familiar to Christian readers.