title: symfony: actAs: { Timestampable: ~ }
body: <p>I've got two little questions:</p>
  
  <pre><code>actAs: { Timestampable: ~ }
  </code></pre>
  
  <p>What the "~" what mean in the code above?</p>
  
  <p>Then, I've seen that tables with <code>actAs: { Timestampable: ~ }</code> have two fields (created_at and updated_at).</p>
  
  <p>Is it possible to bind the updated_at field to a particular field (I update this field, then updated_at get a new value) ?</p>