When you group data by a specific column, the grid combines data rows into groups. Each group contains rows with the same value in the field (column) for which grouping has been applied. Use the GroupInterval property to change the logic used to decide which rows should be grouped together. For instance, for a column that displays date/time information, you can set its GroupInterval property to ColumnGroupInterval.DateRange. In this case, when grouping is applied against this column, the data rows will be combined into groups according to their date value compared with the current system date ("Today", "Yesterday", etc.).