cell time FormatString

Hello, Ebrahim,   

Setting the GridViewDateTimeColumn.FormatString property controls how the cells will be formatted when the cell is not in edit mode. For the editor's format, set the Format property of the column to Custom and the CustomFormat property of the column to a desired format: 

            GridViewDateTimeColumn column = (GridViewDateTimeColumn)this.radGridView1.Columns["OrderDate"]; 
            column.FormatString = "{0:hh.mm}";
            column.Format = DateTimePickerFormat.Custom;
            column.CustomFormat = "hh.mm";

https://docs.telerik.com/devtools/winforms/controls/gridview/columns/column-types/gridviewdatetimecolumn

I hope this information helps. If you need any further assistance please don't hesitate to contact me. 

Regards,
Dess | Tech Support Engineer, Principal
Progress Telerik