Rosh Hashanah, the Jewish New Year, 2018 begins on the sunset of Sunday, Spetember 9 and ends in the evening of Tuesday, September 11.
In the Hebrew calendar it falls on 1 and 2 Tishrei.
See also:
Rosh Hashanah Overview
Rosh Hashanah Recipes
Shofar Blowing
Yom Kippur