How to set default value for GridDateTimeColumn in WinForms DataGrid (SfDataGrid) when the underlying date value is null?

public Form1()
{
    InitializeComponent();
 
    this.sfDataGrid1.CellRenderers["DateTime"] = new CustomDateTimeRenderer(this.sfDataGrid1);
}
 
public class CustomDateTimeRenderer : GridDateTimeCellRenderer
{
    SfDataGrid DataGrid { get; set; }
    public CustomDateTimeRenderer(SfDataGrid dataGrid)
    {
        this.DataGrid = dataGrid;
    }
    protected override void OnRender(Graphics paint, Rectangle cellRect, string cellValue, CellStyleInfo style, DataColumnBase column, RowColumnIndex rowColumnIndex)
    {
        if(string.IsNullOrEmpty(cellValue))
        {
            var recordIndex = this.TableControl.ResolveToRecordIndex(rowColumnIndex.RowIndex);
            object data = null;
            if (recordIndex < 0)
                return;
            if (this.DataGrid.View.TopLevelGroup != null)
            {
                var record = this.DataGrid.View.TopLevelGroup.DisplayElements[recordIndex];
                if (!record.IsRecords)
                    return;
                data = (record as RecordEntry).Data;
            }
            else
            {
                data = this.DataGrid.View.Records.GetItemAt(recordIndex);
            }
 
            if (data != null)
            {
                this.DataGrid.View.GetPropertyAccessProvider().SetValue(data, column.GridColumn.MappingName, DateTime.Now);
            }
        }
 
        base.OnRender(paint, cellRect, cellValue, style, column, rowColumnIndex);
    }
}