Exercise 3 solution

    from datetime import datetime, timezone, timedelta

    tz = timezone(timedelta(hours=5, minutes=30))
    t = datetime(2026, 3, 5, 9, 0, tzinfo=tz)
    moved = t.astimezone(timezone.utc)
    relabelled = t.replace(tzinfo=timezone.utc)
    print(t.isoformat())
    print(moved.isoformat())
    print(relabelled.isoformat())
    print(t == moved, t == relabelled)
    print(relabelled - t)

Output (run, and exactly as shown):

    2026-03-05T09:00:00+05:30
    2026-03-05T03:30:00+00:00
    2026-03-05T09:00:00+00:00
    True False
    5:30:00

Explanation: astimezone keeps the instant and changes how it is written, so
the result is equal to the original. replace(tzinfo=...) keeps the clock
reading and swaps the label, which names a different instant. Here the
relabelled value is 5 hours 30 minutes later than the original. Use replace
only to attach a zone to a naive value whose zone you know; use astimezone to
convert an aware value.