The Holiday of Rosh Hashanah and the Lunar Calendar

Happy New Year! We are about to celebrate the Jewish year of 5779, which is believed to be the time since the creation of the earth, calculated by rabbis who added up the ages of everybody mentioned in the Old Testament. As mentioned above the holiday which begins on the first day of Tishre occurs at the beginning of the seventh month of the year as ordained by G-d through Moses, and not the first, which is Nisan. The date changes each year on the Gregorian or Civil calendar because of the vagaries of the Jewish religious calendar which operates both according to the phases of the moon and to the movement of the sun around the earth.