title: Converting string to moment gives wrong year
body: <p>This is my code in js:</p>
  
  <pre><code>var x = "2017-1-2";
  var y = moment(x, "yyyy-MM-DD")
  </code></pre>
  
  <p>And when I watch y in console this is what it is:</p>
  
  <p><a href="https://i.stack.imgur.com/OtQWd.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/OtQWd.png" alt="enter image description here"></a></p>
  
  <p>As you can see, the _d has the correct day and monthe, but the wrong year. Why is this happening and how to fix it? I use that value to send it to server via ajax and the wrong year gets sent.</p>