The papacy is the oldest non-hereditary monarchy in the world. Over its two thousand year history, it has influenced the lives of billions of people, Christian and non-Christian. The influence of the papacy has by no means been limited to the religious sphere, however. Popes have been directly involved in setting up the Holy Roman Empire, the demise of paganism and global politics. As patrons of the arts, popes have commissioned some of the finest masterpieces, including the Sistine Chapel and St Peter's Basilica. In the area of the politics, Pope Alexander VI divided the map of the newly discovered territories of the Americas in the late 15th century. In the area of temporal calculation, a sixth-century pope changed the global calander and in the 16th century, Pope Gregory XII reformed the calendar of Julius Caesar. From the earliest forays of the Muslim world westwards, the Popes have launched crusades to stop their advance. Most recently, Pope John Paul II, in his 25-year pontificate, has raised the profile of the papacy immeasurably.