title: find most recent date in pandas dataframe
body: <p>I have a csv file, that I read into a pandas dataframe.  The date and times are listed in a column "DateTime".  I want to find the most recent and the least recent date to create an index to create a time series graph.  Does pandas have a function that will return the most recent and the least recent date?  </p>
  
  <p>Edit:<br>
  I already tried using min and max.  They give incorrect answers. </p>
  
  <pre><code>&gt;&gt;&gt; f['Start Date']  
  Trip ID  
  4576       8/29/2013 14:13  
  4607       8/29/2013 14:42  
  4130       8/29/2013 10:16  
  4251       8/29/2013 11:29  
  4299       8/29/2013 12:02  
  4927       8/29/2013 18:54  
  4500       8/29/2013 13:25  
  4563       8/29/2013 14:02  
  4760       8/29/2013 17:01  
  4258       8/29/2013 11:33  
  4549       8/29/2013 13:52  
  4498       8/29/2013 13:23  
  4965       8/29/2013 19:32  
  4557       8/29/2013 13:57  
  4386       8/29/2013 12:31  
  ...  
  198757     2/28/2014 20:40  
  198760     2/28/2014 20:59  
  198761     2/28/2014 20:59  
  198763     2/28/2014 21:32  
  198764     2/28/2014 21:32  
  198765     2/28/2014 21:34  
  198766     2/28/2014 21:41  
  198767     2/28/2014 21:50  
  198768     2/28/2014 21:54  
  198770     2/28/2014 22:19  
  198771     2/28/2014 22:15  
  198772     2/28/2014 22:38  
  198773     2/28/2014 22:45  
  198774     2/28/2014 23:01  
  198775     2/28/2014 23:20  
  Name: Start Date, Length: 144015, dtype: object  
  &gt;&gt;&gt; min(f['Start Date'])  
  '1/1/2014 0:14'  
  &gt;&gt;&gt; max(f['Start Date'])  
  '9/9/2013 9:59'  
  </code></pre>