title: How to get data in DateTime format from plot with Events in python?
body: <p>I have data in iPython <code>DataFrame</code> like this</p>
  
  <pre><code>    Date                        X           Y           Z
  0   2015-11-30 20:23:05.556     281.764900  -43.895060  8.714666
  1   2015-11-30 20:23:05.757     192.519990  -44.636436  1.720552
  2   2015-11-30 20:23:05.958     149.030600  -45.098050  1.958352
  3   2015-11-30 20:23:06.171     140.707600  -44.622448  1.510729
  4   2015-11-30 20:23:06.366     139.154890  -45.154003  4.783974
  5   2015-11-30 20:23:06.564     138.875140  -44.790306  2.266093
  </code></pre>
  
  <p>The <code>dtypes</code> of the columns are these:</p>
  
  <pre><code>Date    datetime64[ns]
  X              float64
  Y              float64
  Z              float64
  dtype: object
  </code></pre>
  
  <p>I set the <code>button_press_event</code> to my <code>fig</code> like this </p>
  
  <pre><code>def onclick(event):
      print 'button=%d, x=%d, y=%d, xdata=%s, ydata=%f'%(
          event.button, event.x, event.y, event.xdata, event.ydata)
  cid = fig.canvas.mpl_connect('button_press_event', onclick)
  </code></pre>
  
  <p>and I want to get data from x axes in <code>Date</code> format or <code>String</code> format, but after click in graph I have just this</p>
  
  <pre><code>button=1, x=152, y=339, xdata=735932.856811, ydata=8.518828
  </code></pre>
  
  <p>How to set output from xdata in <code>String</code>?</p>