title: Truncating timestamps
body: <p>Let's suppose I have a timestamp variable:</p>
  
  <pre><code>select timestamp '2011-02-24 08:30:42 +06:00' from dual;
  </code></pre>
  
  <p>Is there any way to "truncate" it to something like</p>
  
  <pre><code>'2011-02-24 08:00:00 +06:00'
  </code></pre>
  
  <p>(I've cut minutes and seconds, but left the timezone)</p>
  
  <p>The target oracle version is 11g r2</p>