1582: Pope Gregory XIII Proclaims the Gregorian Calendar
On February 24, 1582, Pope Gregory XIII officially introduced the Gregorian calendar. This major reform, via the papal bull *Inter gravissimas*, corrected the Julian calendar's accumulated errors. The old system caused the vernal equinox and Easter's date to drift. The new calendar established a more precise leap year rule, ensuring better astronomical alignment. It eventually became the global standard, shaping our modern timekeeping.
Source: gemini