title: mongodb Get the difference of days from dates having different years
body: <p>I am trying get the difference of days between two dates having different years. Like difference of days between 2015-12-26 and 2016-05-16.
  In SQL I would get this below code.</p>
  
  <pre><code>DECLARE @s DATE ='2015-12-26',@t DATE ='2016-05-16'
  SELECT DATEDIFF(N,@s,@d)
  </code></pre>
  
  <p>Can someone help me to convert this SQL Code in mongodb?</p>