Try this:

Regex r = new Regex(".*\\[D\\].*", RegexOptions.IgnoreCase | RegexOptions.Multiline);
        MatchCollection mcInformation = r.Matches(originalText.ToString());

        List<string> listInformation = new List<string>();
        foreach (Match objM in mcInformation)
        {
            listInformation.Add(objM.ToString().Replace("\r",""));

            if (objM.ToString().Contains("START SHOP"))
            {
                Regex rStartDates = new Regex("((?:(?:[0-2]?\\d{1})|(?:[3][01]{1}))[-:\\/.](?:[0]?[1-9]|[1][012])[-:\\/.](?:(?:\\d{1}\\d{1})))(?![\\d])", RegexOptions.IgnoreCase | RegexOptions.Multiline);
                Match mStartDates = rStartDates.Match(originalText.ToString());

                if (mStartDates.Success)
                {
                    string strStartDate = mStartDates.Groups[0].ToString();
                }
            }

            if (objM.ToString().Contains("STOP SHOP"))
            {
                Regex rStopDates = new Regex("((?:(?:[0-2]?\\d{1})|(?:[3][01]{1}))[-:\\/.](?:[0]?[1-9]|[1][012])[-:\\/.](?:(?:\\d{1}\\d{1})))(?![\\d])", RegexOptions.IgnoreCase | RegexOptions.Multiline);
                Match mStopDates = rStopDates.Match(originalText.ToString());

                if (mStopDates.Success)
                {
                    string strStopDate = mStopDates.Groups[1].ToString();
                }
            }
        }