title: Must be a unixtime or a date/time representation parseable by strtotime
body: <p>Why I have this error when run the graph api code for facebook in c#?</p>
  
  <pre><code>(OAuthException - #100) Must be a unixtime or a date/time representation parseable by strtotime()
  </code></pre>
  
  <p>my graph Api code is:</p>
  
  <pre><code>https://graph.facebook.com/v2.1/687925031280154/feed?since=1391244171
  </code></pre>
  
  <p>but the same code return the correct result when I use on: <code>developers.facebook.com/tools/explorer/</code></p>