title: Difference between two dates in Pandas DataFrame
body: <p>I have many columns in a data frame and I have to find the difference of time in two column named as <code>in_time</code> and <code>out_time</code> and put it in the new column in the same data frame.</p>
  
  <p>The format of time is like this <code>2015-09-25T01:45:34.372Z</code>.</p>
  
  <p>I am using Pandas DataFrame.</p>
  
  <p>I want to do like this:</p>
  
  <pre><code>df.days = df.out_time - df.in_time
  </code></pre>
  
  <p><br>
  I have many columns and I have to increase 1 more column in it named days and put the differences there.</p>