"What: It is the birthday of the universe, the day G‑d created Adam and Eve, and it’s celebrated as the head of the Jewish year.
When: The first two days of the Jewish new year, Tishrei 1 and 2, beginning at sundown on the eve of Tishrei 1. Rosh Hashanah 2019 begins at sundown on September 29 and continues through nightfall on October 1.
How: Candle lighting in the evenings, festive meals with sweet delicacies during the night and day, prayer services that include the sounding of the ram’s horn(shofar) on both mornings, and desisting from creative work." Chabad.