Gregorian calendar
The Pope's instruction only applied to the Catholic Church, countries made their own laws. But Europe's Catholic countries decided to follow his lead. Spain, Portugal, and Italy started to use the new calendar on Friday, October 15, 1582, following Julian Thursday, October 4, 1582. In Europe's Protestant countries, people feared that the new calendar was an attempt by the Catholic Church to silence their movement.  Since the Great Schism, Europe's Eastern Orthodox churches also ignored the Pope's decision and many continue to use the Julian calendar even today.