title: Moment js getting next date given specified week day
body: <p>I seem to have a bit of a problem getting the previous Monday given a particular date. I'm trying to use Moment js for the task. Obviously, I can do it by hand, but found it curious that I couldn't get it to work using the example in the moment.js documentation on their website: <a href="http://momentjs.com/docs/#/get-set/day/">http://momentjs.com/docs/#/get-set/day/</a>.</p>
  
  <p>I was trying something like:</p>
  
  <pre><code>moment([2013, 08, 15, 15, 20]).day(-1).format('ddd, MMM DD')
  </code></pre>
  
  <p>which results in the 'two days ago' date, that being September 13 instead of the expected September 9th.</p>
  
  <p>Does anybody have a clue here? Thanks.</p>