title: Add a decimal year to a moment.js date
body: <p>How can I add a decimal/float value to a moment.js date object?</p>
  
  <pre class="lang-js prettyprint-override"><code>moment('2017-09-20').add(1.234, 'years');
  </code></pre>
  
  <p>does only change the year and month, not the day. I was expecting that moment will calculate the correct date of <code>'2017-09-20'</code> plus one year plus the nearest day of the 0.234th of the year 2018. But instead it prints out <code>'2017-11-20'</code>.</p>