The problem is, should you take 1582, 1752, or some other year for the cutoff? If you receive a bare date from anywhere within the Gregorian calendar transition

The problem is, should you take 1582, 1752, or some other year for the cutoff? If you receive a bare date from anywhere within the Gregorian calendar transition, there's no foolproof way to know which calendar it's using. Better to treat dates that old as the social problem that they are, and not try to decree a one true interpretation that will fall flat in most contexts. (And if you do need to interpret old dates, consider adding explicit calendar-type annotations to your dates, and especially make sure they align with the calendar(s) your sources are truly using.)