主题：时间导入问题

无语，你做的例子根本就没有问题，根本就不需要处理。

Forms("主界面").Open()
MainTable = Tables("主界面")

Dim dlg As new OpenFileDialog
dlg.Filter= "Excel文件|*.xls"
If dlg.ShowDialog = DialogResult.Ok Then
    Dim xh,sjh,rq1,rq,sj,js,zwh As String
    application.DoEvents
    Dim Book As New XLS.Book(dlg.FileName)
    Dim Sheet As XLS.Sheet = Book.Sheets(0)
    StatusBar.Message1= "正在导入数据,请稍候"
    StatusBar.ProgressBar.Maximum = sheet.Rows.Count
    StatusBar.ProgressBar.Minimum = 0
    StatusBar.ProgressBar.Visible =True
    application.DoEvents
    If sheet(0,0).text <> "机考安排表" Or sheet(2,0).text <> "姓名" Or sheet(2,1).text <> "学号" Or sheet(2,2).text <> "试卷号" Or sheet(2,3).text <> "试卷名称" Then
        MessageBox.Show("您的数据源不符合国家开放大学报表平台的数据格式,不能导入学生信息表数据!", "提示")
    Else
        DataTables("考试数据表").StopRedraw
        For i As Integer = 3 To sheet.Rows.Count -1
            xh = sheet(i,1).text
            sjh = sheet(i,2).text
            rq = sheet(i,6).text
            sj = sheet(i,7).text
            js = sheet(i,8).text
            zwh = sheet(i,9).text
           
            Dim dr As DataRow =  DataTables("考试数据表").find("学号 = '" & xh & "' and 试卷号 = '" & sjh & "'")
            If dr IsNot Nothing Then
                dr("日期") = rq
                dr("时间") = sj
                dr("教室") = js
                If zwh <> "" Then
                    dr("座位号") = CInt(zwh)
                End If
            End If

            StatusBar.ProgressBar.Value = i
            StatusBar.Message2= Math.Ceiling(i/sheet.Rows.Count * 100) & "%"
            application.DoEvents
        Next
        DataTables("考试数据表").ResumeRedraw
    End If
End If

With Tables("考试数据表")
    For i As Integer = 0 To .Rows.Count - 1
        .Rows(i)("起始时间") = Left(.Rows(i)("时间"),5)
        .Rows(i)("结束时间") = Right(.Rows(i)("时间"),5)
        .Rows(i)("短日期") = Right(.Rows(i)("日期"),2) & "日"
    Next
End With

For Each r As Row In Tables("考试数据表").Rows
    Dim st As String = r("起始时间")
    If st.EndsWith("-") Then
        r("起始时间") = "0" & r("起始时间").trim("-")
    End If
Next

MessageBox.Show("祝贺你!机考数据导入成功!")
StatusBar.Reset()

 你的例子无法体现你的问题啊。

 做一个完整的可以测试的例子发上。

 要不你就单独用代码处理一下，如下

For Each dr As DataRow In DataTables("考试数据表").DataRows
    If dr.IsNull("日期") Then
        dr("短日期") = Nothing
    Else
        Dim d As Date
        If Date.TryParse(dr("日期"), d) Then
            dr("短日期") = d.Day & "日"
            dr("日期") = format(d, "yyyy-MM-dd")
        End If
    End If
Next