title: Midnight in UTC time zone with unix timestamp
body: <p>I was looking for a numeric representation for a date and unix time for midnight (in UTC) seems to be reasonable choice for that. However, as I'm not sure in my math skills, so is</p>
  
  <pre><code>date = date - date % (24 * 60 * 60);
  </code></pre>
  
  <p>where <code>date</code> is unix timestamp, the way to do that? Is there any simpler method?</p>