/// <summary>
        /// Gets the date of the most recent tariff on the specified meter, used when creating a new tariff.
        /// </summary>
        /// <param name="meterId"></param>
        /// <returns>JSON representation of date string, wrapped in EMResponse</returns>
        public string getMinimumTariffDate(int meterId)
        {
            EMResponse response = new EMResponse();
            try
            {
                tariffMgr = new TariffManager();
                response.data = EMConverter.fromObjectToJSON(tariffMgr.getMinimumTariffDate(meterId));
                response.status = ok;
            }
            catch (Exception e)
            {
                response.status = error;
                response.data = e.Message;
            }

            return EMConverter.fromObjectToJSON(response);
        }