Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Count > 1 Then Exit Sub
If Target.Column <> 1 Then Exit Sub
m = Month(Now)
d = Day(DateSerial(Year(Date), Month(Date) + 1, 0))
x = Day(Target.Value) + 1
If Target.Value <= d And Target.Value >= 1 Then Target = m & "月" & x & "日"
End Sub