I am having a hard time figuring things out in formatting the date.
Basically I expect that I can use the DisplayValueFormat of RadGridDatePicker in DataGridDateColumns. As what they said here: The DataGridDateColumns is used to represent DateTime objects. It uses the RadDatePicker control to pick a value in EditMode http://docs.telerik.com/windows-universal/controls/raddatagrid/columns/datagrid-datecolumn.
http://docs.telerik.com/windows-universal/controls/raddatepicker-and-radtimepicker/properties-and-configuration/raddatetimepickers-properties-pickerproperties