def datetime_to_float(datetime):
    """
    SOPC_DateTime* (the number of 100 nanosecond intervals since January 1, 1601)
    to Python time (the floating point number of seconds since 01/01/1970, see help(time)).
    """
    nsec = datetime[0]
    # (datetime.date(1970,1,1) - datetime.date(1601,1,1)).total_seconds() * 1000 * 1000 * 10
    return (nsec - 116444736000000000)/1e7