DataGrid:需加DataFormatString
<asp:BoundColumn DataFormatString="{0:yyyy-MM-dd}" DataField="iaptraedte" ReadOnly="True" HeaderText="结训日期"></asp:BoundColumn>


GridView:需加HTMLEncode 和 DataFormatString<asp:BoundField  HtmlEncode=false  DataField="trasdt"DataFormatString="{0:yyyy-MM-dd}"   HeaderText="开训日期" />