The Jewish year that began at Rosh Hashanah in September 2023 was 5784.
Rosh Hashanah 5784 began at sunset on September 15, 2023, and continued through September 17 in the Diaspora. It began on 1 Tishrei, the first day of the Hebrew calendar’s civil year. Because Jewish dates begin at sunset, the holiday started on the evening before the daytime date often shown on calendars.
The Hebrew calendar is lunisolar: its months follow lunar cycles, while leap-month adjustments keep the calendar aligned with the solar year. That is why Rosh Hashanah moves through September and October in the Gregorian calendar rather than falling on one fixed date.
The number 5784 refers traditionally to the years since the creation of the world, according to the standard Jewish era. It is not the same as the Gregorian year 2023, and the two systems overlap across much of the year. The preceding Hebrew year was 5783, while 5785 began at the next Rosh Hashanah in October 2024.