Rosh Hashanah is celebrated 163 days after the first day of Passover. Today, September 5, is the earliest date the new year can fall and happened last in 1899. The lastest date it can fall is October 5 which will happen next in 2043. Mark it on your planner.
The term, Rosh Hashanah does not appear in the Torah, but is found once in the Bible where it is a general reference to the beginning of the year.
Ezekiel 40:1
In the twenty-fifth year of our exile, at the beginning of the year, on the tenth of the month, in the fourteenth year after the fall of the city—on that very day the hand of the Lord was on me and He took me there.
It is neither right nor wrong to celebrate Rosh Hashanah. As our Gregorian calendar is near the final quarter of our year, Rosh Hashanah gives us a good reminder to put our trust in Jesus Christ for a sweet year.