When is Rosh Hashanah (Jewish New Year) and how long does it last?

 from ALMANAC dot-com (Old Farmer's Almanac) --

This two-day Jewish celebration of the New Year 

literally translates to “head of the year” in Hebrew. 

It is observed on the first and second days of 

the Jewish month of Tishrei, the first month in the civil calendar. 

In 2021, it begins at sundown, Monday, September 6, 

and ends at sundown, Wednesday, September 8.