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.
The calendar system developed by the Olmec civilization was adopted by most early Mexican cultures. This calendar, known as the Mesoamerican Long Count calendar, played a significant role in the civilizations that followed, such as the Maya and Aztec.