title: Compare two NSDates
body: <p>How can I compare two NSDates and return the amount of time between them.</p>
  
  <p>For example:</p>
  
  <pre><code>2010-06-20 14:29:41 -0400
  2010-06-20 14:53:29 -0400
  </code></pre>
  
  <p>should return something like: <code>23</code> or <code>24</code>(minutes), rounding the seconds because I don't really need the seconds.</p>