I run the coding, it was worked.
but it is not worked when I re-opened the file.
Use "F8" step to active the coding, it is also no responese

Sub Worksheet_Change(ByVal Target As Range)
Application.EnableEvents = True
If Target.Column = 1 Then
       If Target.Row >= 2 Then 
          Target = Cstr(Format(Target,"DD MMM YYYY")
       End if 
    End if 
End Sub