def get_simple_nominal_time(data_object, sample, delta=None):
    """
    Returns a float.

    Returns the nominal time of the specified sample number without
    using any time packet packet information, i.e. only the header
    information is used.
    """
    hdr = data_object['HEADER']
    if delta is None:
        delta = hdr['TIME']['DELTA']
    start = hdr['TIME']['START']
    return start + delta * sample