590- 604 CE - Gregory the Great became pope and gained control of Rome around the seventh century CE. Gregory organized Rome and its surrounding territories into a system of government known as the Papal States. Gregory probably established control in Rome to prevent further damage from the Lombards who had warred with Rome in the preceding century. Gregory successfully converted England and many Germanic peoples to Christianity by sending missionaries abroad. Gregory is also well known for his correction to the Julian Calendar. The Julian calendar provided for an extra day each February, however Gregory amended the calendar to the current system in which certain years do not have leap years based on a fixed schedule that allows the calendar to stay synchronized with the seasons to a very high degree of accuracy.