Exercise 2 solution

    from datetime import datetime, timezone, timedelta

    def compare(a, b):
        try:
            if a < b:
                return "before"
            if a > b:
                return "after"
            return "same instant"
        except TypeError:
            return "cannot compare"

    n1 = datetime(2026, 3, 5, 9, 0)
    n2 = datetime(2026, 3, 5, 10, 0)
    u1 = datetime(2026, 3, 5, 9, 0, tzinfo=timezone.utc)
    e1 = datetime(2026, 3, 5, 4, 0, tzinfo=timezone(timedelta(hours=-5)))
    e2 = datetime(2026, 3, 5, 9, 0, tzinfo=timezone(timedelta(hours=-5)))
    print(compare(n1, n2))
    print(compare(u1, e1))
    print(compare(u1, e2))
    print(compare(e2, u1))
    print(compare(n1, u1))
    print(n1 == u1)

Output (run, and exactly as shown):

    before
    same instant
    before
    after
    cannot compare
    False

Explanation: two naive values compare by their clock readings. Two aware
values compare by the instant they name, so 04:00 at -5 hours equals 09:00
UTC, while 09:00 at -5 hours is five hours later than 09:00 UTC. Ordering a
naive value against an aware one raises TypeError, which the function turns
into a message. Note that == does not raise: it quietly returns False, so an
equality test cannot tell you that the two kinds were mixed.