The Julian calendar that was used prior to the Gregorian calendar in Europe had a small problem—the length of a year was off by a little over 11 minutes. As a result, the date of the spring equinox go slowly pushed back from March 21 to March 11. When Pope Gregory XIII instituted his calendar , he just dropped 10 days from October to account for it. Learn how the Gregorian calendar , introduced in 1582 , corrected the inaccuracies of the Julian calendar and why some countries skipped days when they switched. See the table of when and how different countries adopted the new calendar system and the variations in different regions. 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. After years of consultation and research, Pope Gregory XIII signed a papal bull in February 1582 promulgating the reformed calendar that came to be known as the Gregorian calendar.
