import datetime

def time_after_time(time_a, time_b):
    time_a_min = time_a.hour * 60 + time_a.minute
    time_b_min = time_b.hour * 60 + time_b.minute
    out_min = time_b_min - time_a_min
    if out_min < 0:
        out_min += 24 * 60
    return datetime.time(out_min / 60, out_min % 60)

print(time_after_time(datetime.time(9, 0), datetime.time(10, 0)))
print(time_after_time(datetime.time(10, 0), datetime.time(9, 0)))

01:00:00
23:00:00