C# จะเช็คค่าวันที่จากฐานข้อมูล แล้วนำมาแสดงค่าคับ มัน Error คับ

 private void dateTimePicker1_ValueChanged(object sender, EventArgs e)
        {
            //sb.Remove(0, sb.Length);
            sb = new StringBuilder();
            sb.Append("SELECT Human.HID,Human.FullName,WorkType.WorkTypeName, ");
            sb.Append(" Human.Telephone,Human.FirstDate,Humanschedule.Date,Humanschedule.HID, ");
            sb.Append(" Humanschedule.Time_IN , Humanschedule.Time_OUT");
            sb.Append(" FROM Human,WorkType,Humanschedule");
            sb.Append(" WHERE (Human.WID = WorkType.WID)");
            sb.Append(" AND (Human.HID=Humanschedule.HID)");
            sb.Append(" AND (Human.IsLeave='0')");
            sb.Append(" AND (Humanschedule.Date=@Date)");
            

            string sqlSearch;
            sqlSearch = sb.ToString();

            com = new SqlCommand();
            com.Parameters.Clear();
            com.Parameters.Add("@Date", SqlDbType.DateTime).Value = dateTimePicker1.Value;
            com.CommandText = sqlSearch;
            com.CommandType = CommandType.Text;
            com.Connection = Conn;
            dr = com.ExecuteReader();
            if (dr.HasRows)
            {
                DataTable dtHuman = new DataTable();
                dtHuman.Load(dr);
                //dgvHumanList.Columns.Clear();
                colName.DataPropertyName = "Fullname";
                ColPosition.DataPropertyName = "WorkTypeName";
                colTel.DataPropertyName = "telephone";
                colStart.DataPropertyName = "FirstDate";
                colIn.DataPropertyName = "Time_IN";
                colOut.DataPropertyName = "Time_OUT";
                dgvHumanList.DataSource = dtHuman;

                dgvHumanList.DataSource = dtHuman;
                int countdt = dtHuman.Rows.Count;
                //MessageBox.Show(Convert.ToString(countdt));
                for (int i = 0; i <= countdt - 1; i++)
                {
                    string dateStr = dtHuman.Rows[i]["FirstDate"].ToString();
                    dateStr = Convert.ToDateTime(dateStr).ToString("yyyyMMdd"); // ใช้การจัดรูปแบบสตริงแทน
                    //MessageBox.Show(dateStr);

                    string sub1 = dateStr.Substring(0, 4);
                    string sub2 = dateStr.Substring(4, 2);
                    string sub3 = dateStr.Substring(6, 2);
                    int sub4 = Convert.ToInt32(sub1) - 543;
                    int sub5 = Convert.ToInt32(sub2);
                    int sub6 = Convert.ToInt32(sub3);

                    //MessageBox.Show(Convert.ToString(sub4));
                    //MessageBox.Show(Convert.ToString(sub5));
                    //MessageBox.Show(Convert.ToString(sub6));

                    DateTime myDate = new DateTime(sub4, sub5, sub6);
                    DateTime ToDate = DateTime.Now;

                    DateDifference dDiff = new DateDifference(myDate, ToDate);
                    //MessageBox.Show(Convert.ToString(dDiff));
                    string totalworkage;
                    totalworkage = Convert.ToString(dDiff);
                    // MessageBox.Show(totalworkage);
                    dgvHumanList.Rows[i].Cells["ColWorkAge"].Value = totalworkage;
                    RunSchedule();


                }
                CountWorkTime();
                fommatdgv();
            }
            else
            {
                MessageBox.Show("ไม่มีข้อมุลตารางงานวันนี้", "ผิดพลาด", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
                dr.Close();
            }
        }