title: how to make self updating clock label in kivy?
body: <p>I want to make a Label which acts as a clock and gets updated every second just as in <a href="https://stackoverflow.com/questions/18923321/making-a-clock-in-kivy">making-a-clock-in-kivy</a> link but in the status bar.</p>
  
  <p>I want the label in <em>status.kv</em> file with <em>id: _tnd</em> to act as a clock. 
  The print statement in the update function (test_gui.py) does work and prints the date and time in the console after every second, but the label is not getting updated. I am pretty much confused right now!. It might be a silly mistake, but How do I do it?</p>
  
  <p>I have 3 files</p>
  
  <ol>
  <li>test_gui.py </li>
  <li>test.kv</li>
  <li>status.kv</li>
  </ol>
  
  <p>test_gui.py file</p>
  
  <pre><code>import time
  from kivy.app import App
  from kivy.clock import Clock
  from kivy.lang import Builder
  from kivy.uix.boxlayout import BoxLayout
  from kivy.properties import ObjectProperty
  from kivy.properties import StringProperty
  
  Builder.load_file('status.kv')
  
  class Status(BoxLayout):
      _change = StringProperty()
      _tnd = ObjectProperty(None)
      def update(self,*args):
          self.time = time.asctime()
          self._change = str(self.time)
          self._tnd.text = str(self.time)
          print self._change
  
  class C(BoxLayout):
      pass
  
  
  class TimeApp(App):
      def build(self):
          self.load_kv('test.kv')
          crudeclock = Status()
          Clock.schedule_interval(crudeclock.update, 1)
          return C()
  
  if __name__ == "__main__":
      TimeApp().run()
  </code></pre>
  
  <p>test.kv file</p>
  
  <pre><code>    &lt;C&gt;:
      BoxLayout:
          orientation: 'vertical'
          BoxLayout:
              Button:
                  text: "Button"
              Label:
                  text: "Label"
          Status:
  </code></pre>
  
  <p>status.kv file</p>
  
  <pre><code>    &lt;Status&gt;:
      size_hint: 1,.1
      _tnd: _tnd
      canvas.before:
          Color:
              rgba: 0,0,0,1
          Rectangle:
              pos: self.pos
              size: self.size
      Label:
          text:'Current Date and Time:'
      Label:
          id: _tnd
          text: root._change +' time'
  </code></pre>