The Gregorian calendar is off by about 1 day every 3000 years. It replaced the Julian calendar that was off by about 1 day every 125 years.
But every calendar has replaced other calendars, and humans have kept track of the passage of time in many different cultures. There’s no way we could “lose” or “gain” 300 years in the course of only 2000. Too many people were keeping track.
The Gregorian calendar is off by about 1 day every 3000 years. It replaced the Julian calendar that was off by about 1 day every 125 years.
But every calendar has replaced other calendars, and humans have kept track of the passage of time in many different cultures. There’s no way we could “lose” or “gain” 300 years in the course of only 2000. Too many people were keeping track.