title: Android: How to get & set directory modification date
body: <p>I'm looking for a way to get a directories modification date. I've tried:</p>
  
  <pre><code>File dir = new File(myDir);
  long mod = dir.lastModified();
  </code></pre>
  
  <p>But it's returning 0.</p>
  
  <p>I'm also looking for a way to set the last modification date of a directory but haven't found anything.</p>
  
  <p>Is there a documented way to do these?</p>