Pope Gregory XIII introduced the Gregorian calendar in 1582 to correct inaccuracies in the Julian calendar, which had caused the spring equinox to drift over time. Ten days were skipped (October 4 was followed by October 15) to realign the civil year with the solar year. The new calendar also improved the leap year system. It was gradually adopted by Catholic countries first, and later by the rest of the world.
The Comtat Venaissin was a territory belonging to the Papal States, located around Avignon in southern France. It was under papal sovereignty from 1274 to 1791, although geographically surrounded by the Kingdom of France. This special status made the region an important administrative and religious center, with its own coinage.
