> Using a Gregorian Date before the calendar was introduced is almost certainly an error.
It's just an extrapolation; using the calendar being used at the considered time would be meaningless for us, e.g. the short-lived french republican calendar [1].
It's just an extrapolation; using the calendar being used at the considered time would be meaningless for us, e.g. the short-lived french republican calendar [1].
[1] https://en.wikipedia.org/wiki/French_Republican_calendar