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
在日常录入EXCEL表格的单元格里 ，我们输入一些一般性的日期内容，如：2017-10-17 或 2017/10/17时，EXCEL会自动识别为日期并按单元格设计格式显示，单元格中存储的值也是日期格式的值。
但我们进行不规范的日期输入时，如在单元格中输入：2017.10.10或2017。10。10或20171010时，EXCEL不会自动识别这些内容为日期，而只会识别为字符串（文本），且在单元格中存储的也只是文本而已。
我们通过编写VBA代码可以轻松解决此问题，让EXCEL完美识别输入的任何日期内容，不管是20171010或2017.10.10还是201711或20170101或2017131都可被正确识别，而且是直接将单元格中存储的值转换为日期值，不仅仅是显示格式的转换。
闲话不说，直接让VBA代码：
(要录入VBA代码，必须通过EXCEL进入VBA编辑器，这部分内容可搜索下)
'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
k = 0
myDate = DateValue(strDATE)
myDate = Format(myDate, "yyyy/m/d")
TryChangeDate2 = myDate
Exit Function
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)
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)
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)
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)
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)
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)
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