This Week in Christian History: Oscar Romero, Gregorian Calendar, Gutenberg Bible

The Gregorian Calendar is Introduced – February 24, 1582

Pope Gregory XIII
A portrait of Pope Gregory XIII (1502-1585), the man who commissioned the creation of the Gregorian calendar. |

This week marks the anniversary of when Pope Gregory XIII officially introduced the calendar that not only bears his name, but is widely used to this day.

In a Papal Bull titled Inter Gravissimas, the Gregorian calendar was introduced as a reform of the commonly used Julian calendar.

"The reason the Julian Calendar had to be replaced was the formula it used to calculate leap years. The Julian formula produced a leap year every four years, which is too many. The Gregorian Calendar uses a much more accurate rule for calculating leap years," explained

While many Catholic nations immediately switched to the new calendar, non-Catholic European countries like England and Russia took far longer to make the change.

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