It is easier for me to answer my question than isolated working code in my complex program. So this is my hack that works inside my program:
private void GridView_CustomDrawEvent(object sender, RowCellCustomDrawEventArgs e)
{
    if(e.Column.FieldName == "CreationDate")
    {
        string date = ((DateTime) view.GetRowCellValue(e.RowHandle, "CreationDate"));
        string displayDate = date.ToShortDateString() + " " time.ToLongTimeString();
        e.DisplayText = displayDate;
    }
}
I catch my DateTime object in CustomDrawCell event and I am translating it to string using two standard methods DateTime.ToShortDateString() and DateTime.ToLongTimeString(). Thanks very much for your time.
solved How to show date in diffrent way in GridView?