I am creating a column chart using NumericSeries. This chart can draw one or more series based off of a checkbox in the UI. When the user checks to show all columns, the X axis labels are the being set to the DateTime values but rather the NumericSeries.Label property:

                   uc_chart.ChartType = Infragistics.UltraChart.Shared.Styles.ChartType.ColumnChart;
                    uc_chart.Data.SwapRowsAndColumns = true;

                    foreach (DataTable dt in ds.Tables)
                    {

                            NumericSeries nts = new NumericSeries();
                                nts.Label = dt.TableName;

                            for (int i = 0; i < dt.Rows.Count; i++)
                            {
                                nts.Points.Add(new NumericDataPoint(
                                    (double)dt.Rows[i]["Value"],
                                    ((DateTime)dt.Rows[i]["Date"]).ToShortDateString(),
                                    false));
                            }

                            uc_chart.Series.Add(nts);

                            if (!checkShowAllColumns.Checked)
                                break;
                       
                    }