1582 Calendar reform

The 1582 Calendar reform, initiated by Pope Gregory XIII, aimed to fix calendar drift caused by previous inaccuracies. The Julian calendar, used since 45 BC, miscalculated the length of the solar year, causing dates to gradually shift relative to seasons. To correct this, Pope Gregory XIII introduced the Gregorian calendar, which shortened the year by 10 days and adjusted leap year rules to better align with the Earth's orbit. Specifically, in October 1582, the calendar skipped 10 days (October 5–14) so that the date matched the actual solar year more accurately. This reform streamlined datekeeping and maintained seasonal consistency.