title: Drop dataframe columns based on if condition in pandas
body: <p>I have the following dataframe</p>
  
  <pre><code> 2001-01-01   2001-01-02            2001-01-03 
     1               0                   8 
  </code></pre>
  
  <p>I want to drop every column, which is smaller than 2001-01-02, i.e. my df should look like this:</p>
  
  <pre><code>  2001-01-02            2001-01-03
            0                   8 
  </code></pre>
  
  <p>Does anybody know how to do it?</p>