title: How to query the last modification date of a file via HTTP on the iPhone using NSHTTPURLResponse?
body: <p>In my iPhone application I need to query the last modification date of an internet <code>.m4a</code> file via <code>HTTP</code>, but I <strong>DON'T</strong> want to downloading it.</p>
  
  <p>I'm reading Apple's documentation about <code>NSURLRequest</code> and <code>NSHTTPURLResponse</code>, but it seems to be all related to downloading the file and not querying it first. Maybe I'm wrong.</p>
  
  <p>How can I know the last modification date of a <code>.m4a</code> file, via <code>HTTP</code>, <strong>WITHOUT</strong> downloading it? </p>
  
  <p>Thanks!</p>