title: Moment JS: Difference of days ignoring the year
body: <p>I am familiar on how to find the difference of two dates given two moment object a and b:</p>
  
  <pre><code>let diffDays = a.diff(b, 'days');
  </code></pre>
  
  <p>What I am having a problem with is ignoring the year. I only want moment a and b to find the difference of days disregarding what year it is.</p>
  
  <p>Example: </p>
  
  <pre><code>a = June 1, 2015
  b = June 5, 1992 //desired outcome 4. Not 4 + 4*365
  
  let diffDays = a.diff(b, 'days')
  </code></pre>
  
  <h2>How would I go about this?</h2>
  
  <p>UPDATE</p>
  
  <p>The scenario that breaks most answers is below:</p>
  
  <pre><code>let c = moment( "January 5, 2015" );
  let d = moment( "December 25" ).year( c.year() );
  console.log(Math.abs( c.diff( d, 'days' ) ));
  </code></pre>
  
  <p>Output: 354
  Desired: 11 </p>
  
  <p>Setting the year to the same looks like it causes issues. Any solution?</p>