def get_period_label(dt, data_frequency):
    """
    The period label for the specified date and frequency.

    Parameters
    ----------
    dt: datetime
    data_frequency: str

    Returns
    -------
    str

    """
    if data_frequency == 'minute':
        return '{}-{:02d}'.format(dt.year, dt.month)
    else:
        return '{}'.format(dt.year)