通过VBA，当在EXCEL单元格中输入任意的日期格式时，都能自动转换为指定的标准格式的日期值

'以下代码都要放到一个sheet的类模块之中
Dim nDate
Private Sub Worksheet_Activate()'加载sheet的事件
    nDate = InputBox("请确定此工作表中第几列为日期型的数据！", "输入数字", "2")
    If nDate = "" Then
        nDate = 2 '--只操作指定的列号的列，目前只操作B列（第2列）
    Else
        nDate = Val(nDate)
    End If
End Sub
Private Sub Worksheet_Change(ByVal Target As Range)'--sheet中任何地方发生数据改变时触发的事件
    If nDate = 0 Then Exit Sub
    If Target.Cells.Column = nDate Then '--如果是第二列才检验文本为日期
        Target.Value = TryChangeDate2(Target.Value)
    End If
End Sub
Public Function TryChangeDate2(ByVal strDATEcome As String) As Variant
    On Error GoTo TryChangeDate2ERR
    Dim strDATE As String
    strDATE = Trim(strDATEcome)
    Dim myDate As Date
    Dim strK As String
    strK = mTrim(strDATEcome)
    Dim k As Integer, nkkkk As Integer
    k = -1
k0:
    k = 0
    myDate = DateValue(strDATE)
    myDate = Format(myDate, "yyyy/m/d")
    TryChangeDate2 = myDate
    Exit Function
k1:
    k = 1
    myDate = DateValue(strDATE)
    myDate = Format(myDate, "yyyy/m/d")
    TryChangeDate2 = myDate
    Exit Function
TryChangeDate2ERR:
    Err.Clear
    If k = 0 Then
        nkkkk = Len(strK)
        Select Case nkkkk
            Case 4
                If InStr(1, strK, ".") = 0 And InStr(1, strK, ",") = 0 And InStr(1, strK, "/") = 0 And InStr(1, strK, "") = 0 And InStr(1, strK, "-") = 0 Then
                    strDATE = Left(strK, 2) & "/" & Mid(strK, 3, 1) & "/" & Mid(strK, 4, 1)
                End If
            Case 5
                If InStr(1, strK, ".") = 0 And InStr(1, strK, ",") = 0 And InStr(1, strK, "/") = 0 And InStr(1, strK, "") = 0 And InStr(1, strK, "-") = 0 Then
                    If Val(Mid(strK, 3, 1)) >= 3 Then
                        strDATE = Left(strK, 2) & "/" & Mid(strK, 3, 1) & "/" & Mid(strK, 4, 2)
                    Else
                        strDATE = Left(strK, 2) & "/" & Mid(strK, 3, 2) & "/" & Mid(strK, 5, 1)
                    End If
                End If
            Case 6
                If InStr(1, strK, ".") = 0 And InStr(1, strK, ",") = 0 And InStr(1, strK, "/") = 0 And InStr(1, strK, "") = 0 And InStr(1, strK, "-") = 0 Then
                    If Left(strK, 1) = "1" Or Left(strK, 1) = "2" Then
                        strDATE = Left(strK, 4) & "/" & Mid(strK, 5, 1) & "/" & Mid(strK, 6, 1)
                    Else
                        strDATE = Left(strK, 2) & "/" & Mid(strK, 3, 2) & "/" & Mid(strK, 5, 2)
                    End If
                    GoTo theEnd
                End If
                    strDATE = Left(strK, 2) & "/" & Mid(strK, 4, 1) & "/" & Mid(strK, 6, 1)
            Case 7
                If InStr(1, strK, ".") = 0 And InStr(1, strK, ",") = 0 And InStr(1, strK, "/") = 0 And InStr(1, strK, "") = 0 And InStr(1, strK, "-") = 0 Then
                    If Val(Mid(strK, 5, 1)) >= 3 Then
                        strDATE = Left(strK, 4) & "/" & Mid(strK, 5, 1) & "/" & Mid(strK, 6, 2)
                    Else
                        strDATE = Left(strK, 4) & "/" & Mid(strK, 5, 2) & "/" & Mid(strK, 7, 1)
                    End If
                Else
                    If Val(Mid(strK, 4, 1)) >= 3 Then
                        strDATE = Left(strK, 2) & "/" & Mid(strK, 4, 1) & "/" & Mid(strK, 6, 2)
                    Else
                        strDATE = Left(strK, 2) & "/" & Mid(strK, 4, 2) & "/" & Mid(strK, 7, 1)
                    End If
                End If
            Case 8
                If InStr(1, strK, ".") = 0 And InStr(1, strK, ",") = 0 And InStr(1, strK, "/") = 0 And InStr(1, strK, "") = 0 And InStr(1, strK, "-") = 0 Then
                    strDATE = Left(strK, 4) & "/" & Mid(strK, 5, 2) & "/" & Mid(strK, 7, 2)
                Else
                    strDATE = Left(strK, 4) & "/" & Mid(strK, 6, 1) & "/" & Mid(strK, 8, 1)
                End If
            Case 9
                If Val(Mid(strK, 6, 1)) >= 3 Then
                    strDATE = Left(strK, 4) & "/" & Mid(strK, 6, 1) & "/" & Mid(strK, 8, 2)
                Else
                    strDATE = Left(strK, 4) & "/" & Mid(strK, 6, 2) & "/" & Mid(strK, 9, 1)
                End If
            Case 10
                strDATE = Left(strK, 4) & "/" & Mid(strK, 6, 2) & "/" & Mid(strK, 9, 2)
        End Select
theEnd:
        GoTo k1
    End If
    TryChangeDate2 = strDATEcome
End Function


Public Function mTrim(ByVal strCome As String) As String
'--此函数的作用是去掉字符串中间的空格
On Error GoTo mTrimErr
    Dim i As Integer, j As Integer
    Dim strLS As String, k As String * 1, strResult As String
    strLS = Trim(strCome)
    strResult = ""
    j = Len(strLS)
    For i = 1 To j
        k = Mid(strLS, i, 1)
        If k <> " " And k <> "　" And VarType(k) <> vbNull And k <> vbNullString Then
            strResult = strResult & k
        End If
    Next
    mTrim = strResult
    Exit Function
mTrimErr:
    Err.Clear
    mTrim = strCome
End Function

'---以上代码可实现在EXCEL指定列（上面指定为B列）中录入日期内容时，任意可识别的日期都会被自动转换成标准日期值，并以日期值存储在单元格中
'---欢迎大家批评指正，如果发现错误，欢迎指正，如有不明子的地方，欢迎交流
'--QQ: 578652607