title: Getting Invalid Day in Date when using moment.js in Mozilla Firefox
body: <p>i'm currently using moment.js library to render dates in real time to my users, but after some tests today, i noticed something really weird, when listing all possible days to the user in Firefox, moment.js fails to add days in the date '2015-09-14'.
  After searching the developers documentation and the internet, i discovered that you have to pass a ISO8601 valid Date or construct by passing explicit information of the date, but the results continue to confuse me.</p>
  
  <p>Here's some code for understanding:</p>
  
  <p>Working case (creating a moment() instance from current time):</p>
  
  <pre><code>var printVar = moment();
  var divInfo  = document.getElementById('calendars');
  divInfo.innerHTML += "&lt;ul&gt;";
  
  for(var i=0; i&lt;40; i++){
      divInfo.innerHTML += "&lt;li&gt; " + printVar.format('DD/MM/YYYY') + " &lt;/li&gt;";            
      printVar = moment(printVar).add(1, 'days');
  }
  
  divInfo.innerHTML += "&lt;/ul&gt;";
  </code></pre>
  
  <p>My Result:</p>
  
  <ul>
  <li>15/10/2015   </li>
  <li>16/10/2015   </li>
  <li>17/10/2015   </li>
  <li>18/10/2015   </li>
  <li>19/10/2015 </li>
  <li>20/10/2015</li>
  </ul>
  
  <p>Weird case #1 (creating a moment() using time with encoding 'YYYY-MM-DD'):</p>
  
  <pre><code>var printVar = moment('2015-09-14');
  
  var divInfo  = document.getElementById('calendars');
  divInfo.innerHTML += "&lt;ul&gt;";
  
  for(var i=0; i&lt;40; i++){
      divInfo.innerHTML += "&lt;li&gt; " + printVar.format('DD/MM/YYYY') + " &lt;/li&gt;";            
      printVar = moment(printVar).add(1, 'days');
  }
  
  divInfo.innerHTML += "&lt;/ul&gt;";
  </code></pre>
  
  <p>My Result:</p>
  
  <ul>
  <li>15/10/2015</li>
  <li>16/10/2015</li>
  <li>17/10/2015</li>
  <li>17/10/2015</li>
  <li>18/10/2015</li>
  <li>19/10/2015</li>
  </ul>
  
  <p>Weird case #2 (creating a moment() using explicit constructor like moment([2015, 8, 14])) return the same result: </p>
  
  <ul>
  <li>15/10/2015</li>
  <li>16/10/2015</li>
  <li>17/10/2015</li>
  <li>17/10/2015</li>
  <li>18/10/2015</li>
  <li>19/10/2015</li>
  </ul>
  
  <p>Firefox version: 40.0.3</p>
  
  <p>Thanks for all the Help!</p>