Return POSIX timestamp corresponding to the datetime instance. The return value is a float similar to that returned by time.time().
datetime.timestamp()
(dt - datetime(1970, 1, 1, tzinfo=timezone.utc)).total_seconds()
timestamp = dt.replace(tzinfo=timezone.utc).timestamp()
timestamp = (dt - datetime(1970, 1, 1)) / timedelta(seconds=1)