The first of the seventh month, announced by the ram's horn — later kept as the civil new year.
A day of rest announced with horn blasts, opening the seventh month and the ten days that lead to the Day of Atonement. Leviticus gives it no explanation at all — just the date, the rest and the noise — which is unusual among the feasts and has left the reason open ever since. In later Jewish practice it became Rosh Hashanah, the head of the civil year.