title: Difference between data type 'datetime64[ns]' and '<M8[ns]'?
body: <p>I have created a TimeSeries in pandas:</p>
  
  <pre><code>In [346]: from datetime import datetime
  
  In [347]: dates = [datetime(2011, 1, 2), datetime(2011, 1, 5), datetime(2011, 1, 7),
  
   .....: datetime(2011, 1, 8), datetime(2011, 1, 10), datetime(2011, 1, 12)]
  
  In [348]: ts = Series(np.random.randn(6), index=dates)
  
  In [349]: ts
  
  Out[349]: 
  
  2011-01-02 0.690002
  
  2011-01-05 1.001543
  
  2011-01-07 -0.503087
  
  2011-01-08 -0.622274
  
  2011-01-10 -0.921169
  
  2011-01-12 -0.726213
  </code></pre>
  
  <p>I'm following on the example from 'Python for Data Analysis' book. </p>
  
  <p>In the following paragraph, the author checks the index type:</p>
  
  <pre><code>In [353]: ts.index.dtype
  
  Out[353]: dtype('datetime64[ns]')
  </code></pre>
  
  <p>When I do exactly the same operation in the console I get:</p>
  
  <pre><code>ts.index.dtype
  dtype('&lt;M8[ns]')
  </code></pre>
  
  <p>What is the difference between two types <code>'datetime64[ns]'</code> and <code>'&lt;M8[ns]'</code> ?</p>
  
  <p>And why do I get a different type?</p>