def _validate_parameters(data, old_start, old_dt, new_start, new_dt, new_npts):
    """
    Validates the parameters for various interpolation functions.

    Returns the old and the new end.
    """
    if new_dt <= 0.0:
        raise ValueError("The time step must be positive.")

    # Check for 1D array.
    if data.ndim != 1 or not len(data) or not data.shape[-1]:
        raise ValueError("Not a 1D array.")

    old_end = old_start + old_dt * (len(data) - 1)
    new_end = new_start + new_dt * (new_npts - 1)

    if old_start > new_start or old_end < new_end:
        raise ValueError("The new array must be fully contained in the old "
                         "array. No extrapolation can be performed.")

    return old_end, new_end