1582 october calendar: The Disappearing Days Implementing the Gregorian calendar

The Disappearing Days Implementing the Gregorian calendar required a reset. Pope Gregory XIII decreed that October 4, 1582 , would be followed not by October 5, but by October 15. The Gregorian calendar reform officially kicked in on October 4, 1582 . Ten days vanished overnight in Catholic countries like Spain, Portugal, Italy, and Poland. Discover why 10 days went missing in October 1582 and how leap year rules keep our calendar aligned with the Earth’s orbit. Discover why 10 days disappeared in October 1582 with our detailed overview of the Gregorian calendar reform. Learn about its impact on society, its historical context, and the global adoption of the new calendar system.