Rosh Hashanah is the Jewish New Year. It occurs 163 days after the first day of passover, in early fall. The holiday occurs between September 5th and October 5th.
Rosh Hashanah marks the beginning of a new season of harvest. Many communities in southwest Asia considered the calendar year to begin with the autumn harvest or rainy season. It was common to celebrate the New Year during this time.
The holiday is a time to reflect upon God's just and omniscient nature. It is a chance to reflect upon one's own actions that year, and to renew one's religious and ethical commitments.