Exercise 1 solution

    from datetime import datetime

    def readings(text):
        found = set()
        for f in ("%d/%m/%Y", "%m/%d/%Y"):
            try:
                found.add(datetime.strptime(text, f).date())
            except ValueError:
                pass
        return sorted(found)

    for t in ["03/04/2026", "13/04/2026", "05/05/2026", "31/02/2026"]:
        r = readings(t)
        verdict = "ambiguous" if len(r) > 1 else ("clear" if r else "invalid")
        print(t, [d.isoformat() for d in r], verdict)

Output (run, and exactly as shown):

    03/04/2026 ['2026-03-04', '2026-04-03'] ambiguous
    13/04/2026 ['2026-04-13'] clear
    05/05/2026 ['2026-05-05'] clear
    31/02/2026 [] invalid

Explanation: a set holds each distinct date once, so a text that reads the
same both ways (05/05/2026) collapses to one date and is safe even though it
fits both formats. Only when two different dates come out is the text truly
ambiguous. 13/04/2026 has only one reading because there is no month 13, and
31/02/2026 fits neither because February never has 31 days.