title: Convert milliseconds timestamp to date from unix command line
body: <p>I know about</p>
  
  <pre><code>date -d @&lt;timestamp in seconds&gt;
  </code></pre>
  
  <p>and</p>
  
  <pre><code>awk '{print strftime("%c", &lt;timestamp in seconds&gt;)}'
  </code></pre>
  
  <p>but what if I have milliseconds. Is there trivial way to do this without dropping the final three characters of the millisecond-timestamp (not that dropping characters is difficult, but I would think there'd be a one-step way for such a straightforward task)?</p>