Exercise 1 solution

    from datetime import datetime, timezone

    def describe(text):
        d = datetime.fromisoformat(text)
        if d.utcoffset() is None:
            return text + " naive"
        utc = d.astimezone(timezone.utc)
        return f"{text} aware offset {d.utcoffset().total_seconds() / 3600} hours utc {utc.isoformat()}"

    for s in ["2026-03-05T09:00:00", "2026-03-05T09:00:00Z",
              "2026-03-05T14:30:00+05:30", "2026-03-05T23:00:00-04:00"]:
        print(describe(s))

Output (run, and exactly as shown):

    2026-03-05T09:00:00 naive
    2026-03-05T09:00:00Z aware offset 0.0 hours utc 2026-03-05T09:00:00+00:00
    2026-03-05T14:30:00+05:30 aware offset 5.5 hours utc 2026-03-05T09:00:00+00:00
    2026-03-05T23:00:00-04:00 aware offset -4.0 hours utc 2026-03-06T03:00:00+00:00

Explanation: the test for "naive" is utcoffset() returning None; checking
tzinfo alone is not quite enough. The "Z" ending is accepted from Python 3.11
and means an offset of zero. The first and third inputs are different text
but the same instant only if both are aware; the naive one carries no offset,
so it gets no UTC conversion (astimezone on a naive value would guess the
machine's own zone, which is why the function avoids it). The last line shows
that converting can change the calendar date: 23:00 at -4 hours is already
the next day in UTC.