title: Open Graph on iOS: how to set expires_time on custom stories to change tense
body: <p>I followed instructions to post a custom story with Open Graph on iOS with this documentation <a href="https://developers.facebook.com/docs/ios/open-graph" rel="nofollow">https://developers.facebook.com/docs/ios/open-graph</a> and it worked fine.</p>
  
  <p>The problem that I'm having is that I don't know how to change the tense of that post, it's always on past tense.</p>
  
  <p>Reading a little bit more, it says on the reference documentation that I should set the attribute "expires_time", but I don't understand how and where.</p>
  
  <p>Any ideas?</p>
  
  <p>Thanks</p>