Gregory XIII

Ugo Boncompagni · 1572 – 1585

Reformed the calendar that bears his name and built the modern seminary system.

Ugo Boncompagni had an illegitimate son before entering the priesthood, a fact that did not prevent him from becoming pope in 1572. His most lasting achievement was the Gregorian calendar, introduced in 1582 to correct the drift in the Julian calendar that had thrown Easter off by ten days. Protestant countries resisted for decades, but eventually everyone adopted it. Gregory also implemented the Council of Trent's decree on seminary education, founding or supporting over twenty seminaries and colleges across Europe, including the Gregorian University in Rome. He sent Jesuit missionaries to China, Japan, and the Americas. Less admirably, he celebrated the St. Bartholomew's Day Massacre of French Huguenots in 1572 with a Te Deum and a commemorative medal, apparently believing it was a legitimate suppression of rebellion rather than a slaughter of civilians.

The Calendar Everyone Uses

The Gregorian calendar is used worldwide today, including by people who have no idea it is named after a pope. It was a practical reform driven by the need to keep Easter in the right season, but it ended up becoming the global standard for civil timekeeping.

Building Seminaries

Trent said priests needed real theological education. Gregory made it happen by funding seminaries across Europe. The system he built became the template for priestly formation that persisted into the twentieth century.

The Massacre Medal

Gregory's celebration of the St. Bartholomew's Day Massacre is indefensible by modern standards. Thousands of French Protestants were murdered, and the pope had a medal struck to commemorate it. Later Catholic historians have tried to explain the context; the reality is that it was a moral failure.