Calendar reforms refer to changes made to the way we organize and measure time, specifically through the structure of calendars. These reforms aim to improve accuracy, consistency, and usability of calendars, often addressing issues like leap years or the alignment of months with seasons. Notable examples include the transition from the Julian calendar to the Gregorian calendar in 1582, which corrected inaccuracies in the previous system. Various cultures have also implemented their own calendar reforms, such as the French Revolutionary calendar introduced during the French Revolution. These reforms often reflect social, political, or religious changes, demonstrating how societies adapt their timekeeping methods to better suit their needs.