internationally the most widely accepted civil calendar
Deutsch: Gregorianischer Kalender, Gregorianische Kalender
English: The Gregorian calendar is the most widely used calendar in the world today. It was first proposed by the Calabrian doctor Aloysius Lilius, and decreed by Pope Gregory XIII, after whom it was named, on February 24, 1582 by papal bull w:Inter gravissimas. It is a reform of the Julian calendar.
Pope Gregory XIII in an early 17th century engraving.
In September 1752, Britain changed from Old Style (O.S.) to New Style (N.S.)