What year did the Gregorian calendar begin?

The calendar was introduced on on 24 February 1582 by Pope Gregory XIII. Further information: The Gregorian calendar was initially decreed, but not implemented, by Pope Gregory XIII on 24 February 1582. On 5 October 1582, the Gregorian calendar was adopted for the first time by Catholic countries such as Italy, Poland, Spain and Portugal. On 10 December 1582, France began using the Gregorian calendar.

Non-Catholic countries such as Scotland, Britain and the latter's colonies still used the Julian calendar up until 1752, and some Asian countries were still using the Julian calendar up until the early twentieth century.