MsgBox "Sep 16 2008 18:40:07.135 = " + Trim(CDate("09 16 2008 18:40:07")) + Chr( 13 ) + "Sep 12 2008 12:24:26.676 = " + Trim(CDate("09 12 2008 12:24:26"))

Format$(Now, "dd mm yyyy hh:nn:ss")

CDate(Mid$(s,  7 ,  4 ) & "-" & Left(s,  2 ) & "-" & Mid$(s,  4 ,  2 ) & " " & Mid$(s,  12 ,  8 ))

Public Sub Main()
    Debug.Print Format$(CDateEx("Sep 16 2008 18:40:07", "mdy"), "d.m.yyyy hh:nn:ss")
    Debug.Print Format$(CDateEx("17 9 2008 18:40:07", "dmy"), "d.m.yyyy hh:nn:ss")
    Debug.Print Format$(CDateEx("18-2008-Sep 18:40:07", "dym"), "d.m.yyyy hh:nn:ss")
    Debug.Print Format$(CDateEx("2008/sep/8 18:40:07", "ymd"), "d.m.yyyy hh:nn:ss")
End Sub
    
Public Function CDateEx(ss As String, Optional ByVal ymd As String = "ymd") As Date
    Dim i As Integer, st As String, sd As String, v As Variant, s As String, k As Integer, _
        m As Integer, d As Integer, y As Integer, j As Integer
    
    ymd = LCase$(ymd)
    i = InStrRev(ss, " ")
    If i Then
        st = Mid$(ss, i)
        ss = Trim$(Left$(ss, i -  1 ))
    End If
    
    ss = Replace(ss, "-", " ")
    ss = Replace(ss, "/", " ")
    ss = Replace(ss, ".", " ")
    
    v = Split(ss, " ")
    On Error GoTo Err_
    For i =  0  To UBound(v)
        s = v(i)
        If Len(s) Then
            k = k +  1 
            If k =  4  Then GoTo Err_
            Select Case Mid$(ymd, k,  1 )
                Case "d"
                    If IsNumeric(s) Then
                        d = CInt(s)
                        If d <  1  Or d >  31  Then GoTo Err_
                    End If
                Case "m"
                    If IsNumeric(s) Then
                        m = CInt(s)
                        If m <  1  Or m >  12  Then GoTo Err_
                    Else
                        s = LCase(Left$(s,  3 ))
                        For j =  1  To  34  Step  3 
                            If s = Mid$("janfebmaraprmayjunjulaugsepoctnovdec", j,  3 ) Then
                                m = (j +  2 ) /  3 : Exit For
                            End If
                        Next j
                    End If
                    If m =  0  Then GoTo Err_
                Case "y"
                    If IsNumeric(s) Then y = CInt(s)
            End Select
        End If
    Next i
    CDateEx = CDate(Format$(DateSerial(y, m, d), "yyyy-mm-dd") & " " & st)
    Exit Function

Err_:
    Err.Raise  513 , , "Строка с датой содержит ошибку"
End Function