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. Gregorian calendar ... The Gregorian calendar is the calendar used in most parts of the world. [1][a] It went into effect in October 1582 following the papal bull Inter gravissimas issued by Pope Gregory XIII, which introduced it as a modification of, and replacement for, the Julian calendar . Imagine waking up in 1582 and finding that ten days had just disappeared from your calendar . The Gregorian calendar reform of 1582 eliminated ten days from Explore the Gregorian calendar reform that skipped 10 days in October 1582 . Learn about the transition from the Julian calendar and how to calculate weekdays.
