title: Adding months to date returns weird numbers
body: <p>I'm trying to add months to my date but the result is pretty weird.</p>
  
  <p>This is what I'm doing:</p>
  
  <pre><code>var date = new Date();
  date = date.setMonth(date.getMonth() + 36);
  </code></pre>
  
  <p>and the outcome is:</p>
  
  <pre><code>1622458745610
  </code></pre>
  
  <p>I don't understand why...</p>