Jewish holiday usually referred to as the "Jewish New Year." It is practical on the first day of Tishrei, the seventh month of the Hebrew calendar. It is ordained in the Torah as "Zicaron Terua".
Rosh Hashanah is the first of the High Holidays or Yamim Noraim / Asseret YemeiTeshuva which are days specifically set aside to focal point on repentance that conclude with the holiday of Yom Kippur. Rosh Hashanah is the begin of the civil year in the Hebrew calendar.
It is the New Year for people, animals, & legal contracts. The Mishnah also sets this day aside as the New Year for calculating calendar years & sabbatical and jubilee years. Jews consider Rosh Hashanah represents either analogically or literally the creation of the World, or Universe.
However, according to one view in the Talmud, that of R. Eleazar, Rosh Hashanah commemorates the conception of man, which entails that five days previous, the 25 of Elul, was the first day of creation of the Universe.