PreGregorian

PreGregorian refers to the time period before the widespread adoption of the Gregorian calendar. This calendar, promulgated by Pope Gregory XIII in 1582, aimed to correct inaccuracies in the Julian calendar, which had been in use since 45 BCE. The Julian calendar's leap year rule, adding a day every four years, caused a slight overcorrection, leading to a drift in the calendar's alignment with the solar year. By the 16th century, this drift had amounted to about ten days.

Before the Gregorian calendar's implementation, various calendars were in use across different regions and cultures. These included different lunisolar calendars, such as the Hebrew calendar, and various other solar or lunar systems. Even within Christian Europe, the Julian calendar was the dominant system for civil and religious purposes, though its inaccuracies were recognized. The transition to the Gregorian calendar was not immediate or universal. Catholic countries adopted it relatively quickly, but Protestant and Orthodox nations often resisted the change for centuries due to religious and political reasons. This period of divergence means that historical dating, especially in the pre-modern era, can be complex, requiring awareness of which calendar was in use in a particular place and time. The preGregorian era, therefore, encompasses a diversity of dating systems and a gradual, often contentious, shift towards a more astronomically accurate reckoning of time.