On October 1793 but usage backdated to 22 September 1793.
France.
"Lobster Thermidor"
The Dominican Republic Flag was adopted on November 6,1844
Great Britain and her colonies adopted the Gregorian calendar on September 14, 1752. The previous day was September 2.
The most widely used calendar in the world, adopted in 1582 to correct errors in the Julian calendar.
In 45 BC.
1945
Several early civilisations adopted the 365 day calendar. Notably the Ancient Egyptians. Certainly before 3000 BC
Their traditional calendar was aligned to the agricultural seasons. After Alexander the great took over Egypt, his Macedonian successors introduced a new calendar, modified later by the Romans as the Julian calendar. A modified Egyptian calendar has remained in use by the Coptic church and peasantry.
1 st January 1752
Pope Gregor XIII introduced the calendar named after him (the Gregorian calendar) in 1582. However, some countries adopted this calendar as late as the 20th. Century.
I do not believe that any other calendar was in use in the United States at any time after the Revolutionary War. England adopted the calendar in 1752, at which time there was not yet any country called the United States--the 13 colonies were part of England.