我使用下面的查询绑定到我的gridview。在gridview中有两个隐藏字段。

sql = "SELECT a.Submission_id ,a.Name,a.Submitted_time  as Normal_submitted_time," +
                    "b.Subject,b.Submitted_time  AS Final_submitted_time FROM a " +
                    " JOIN b ON a.Submission_id = b.Submission_id ";

  <asp:HiddenField ID="HiddenFieldNormalSubmittedTime" runat="server" Value='<%#Eval("Normal_submitted_time") %>'/> 
                       <asp:HiddenField ID="HiddenFielFinalSubmittedTime" runat="server" Value='<%#Eval("Final_submitted_time ") %>'/> 

string HiddenFieldNormalSubmittedTime = Convert.ToString(((HiddenField)gvrow.FindControl("HiddenFieldNormalSubmittedTime")).Value);
string HiddenFieldFinalSubmittedTime = Convert.ToString(((HiddenField)gvrow.FindControl("HiddenFielFinalSubmittedTime")).Value);

hiddenfieldnormalsubmittedtime的值为
2020年6月12日晚上10:20:51
hiddenfieldfinalsubmittedtime的值=
2020年6月17日下午12:30:58
但是当将同一个查询更改为left join时

sql = "SELECT a.Submission_id ,a.Name,a.Submitted_time  as Normal_submitted_time," +
                    "b.Subject,b.Submitted_time  AS Final_submitted_time FROM a " +
                    " JOIN b ON a.Submission_id = b.Submission_id ";

hiddenfieldfinalsubmittedtime的格式更改为
06/17/2020 13:12:55
hiddenfieldnormalsubmittedtime保持不变。原因是什么？在将eval绑定到hiddenfield时，是否可以将其设置为通用格式（12-06-2020 10:20:51 pm）？