title: Pandas Dataframe line plot display date on xaxis
body: <p>Compare the following code:</p>
  
  <pre><code>test = pd.DataFrame({'date':['20170527','20170526','20170525'],'ratio1':[1,0.98,0.97]})
  test['date'] = pd.to_datetime(test['date'])
  test = test.set_index('date')
  ax = test.plot()
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/H6gom.png" rel="noreferrer"><img src="https://i.stack.imgur.com/H6gom.png" alt="enter image description here"></a></p>
  
  <p>I added <code>DateFormatter</code> in the end:</p>
  
  <pre><code>test = pd.DataFrame({'date':['20170527','20170526','20170525'],'ratio1':[1,0.98,0.97]})
  test['date'] = pd.to_datetime(test['date'])
  test = test.set_index('date')
  ax = test.plot()
  ax.xaxis.set_minor_formatter(dates.DateFormatter('%d\n\n%a')) ## Added this line
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/yMqx1.png" rel="noreferrer"><img src="https://i.stack.imgur.com/yMqx1.png" alt="enter image description here"></a></p>
  
  <p>The issue with the second graph is that it starts on <code>5-24</code> instead <code>5-25</code>. Also, <code>5-25</code> of 2017 is Thursday not Monday. What is causing the issue? Is this timezone related? (I don't understand why the date numbers are stacked on top of each other either)</p>