title: How to display date with human language like "Today at xx:xx pm", "Yesterday at xx:xx am"?
body: <p>I have a date "2014-07-02 20:57:38 +0000" and I want to format it as "Today at 8:57 pm".
  I want that if a string is yesterday, then display it as "Yesterday at 9:00 am". If it is neither today or yesterday, just show the actually date like "27/6 at 7:53 pm".</p>
  
  <p>I was able to get the time with format like "8:57 AM" with the code below.</p>
  
  <pre><code>            var formatter : NSDateFormatter = NSDateFormatter()
              formatter.dateFormat = "h:mm a"
  
              // message.createdAt is the date
              let dateString = formatter.stringFromDate(message.createdAt)
              println(dateString)
  
              //output = 8:57 AM
  </code></pre>
  
  <p>However, when I use the following code, it returns a blank string.</p>
  
  <pre><code>            var formatter : NSDateFormatter = NSDateFormatter()
              formatter.dateFormat = "h:mm a"
              formatter.doesRelativeDateFormatting = true  //&lt;-- This doesn't work
  
              let dateString = formatter.stringFromDate(message.createdAt)
              println(dateString)
  
              //output = (nothing, its a blank string)
  </code></pre>
  
  <p>How do I make this work and display "Today" or "Yesterday" in Swift?</p>