Why do Catholics and Orthodox celebrate Easter on different dates?

AI Briefing

• – The Eastern Orthodox Church uses the Julian calendar, which is 13 days behind the Gregorian calendar used by the Catholic Church.
• – The Julian calendar was introduced by Julius Caesar in 45 BCE, while the Gregorian calendar was introduced by Pope Gregory XIII in 1582.
• – The difference in calendars is the reason for the difference in Easter dates, as Easter is tied to the Jewish holiday of Passover and is celebrated on the first Sunday after the full moon following the vernal equinox.