/// <summary>
        /// Gets the message date/time as an ISO 8601 formatted string.
        /// </summary>
        /// <returns>The message date/time as an ISO 8601 formatted string.</returns>
        private string GetIsoDateString()
        {
            if (this.hasTime())
            {
                DateTime time = MessageUtils.FromUnixTime(this.getTime());
                return(time.ToString("s", CultureInfo.InvariantCulture));
            }

            return(null);
        }