title: how to use NSDateFormatter to see "Today" string
body: <p>apple use it in the messages app for today messages 
  Today 11:45 AM
  Yesterday 11:45 AM</p>
  
  <p>i see it in the apple developer site</p>
  
  <blockquote>
    <p>To specify a custom fixed format for a date formatter, you use
    setDateFormat:. The format string uses the format patterns from the
    Unicode Technical Standard #35. The version of the standard varies
    with release of the operating system:</p>
    
    <p>Calendar Fields</p>
    
    <p>fields ( alias | (field*, special*)) > field ( alias | (displayName?,
    relative*, special*)) ></p>
    
    <p>Translations may be supplied for names of calendar fields (elements of
    a calendar, such as Day, Month, Year, Hour, and so on), and for
    relative values for those fields (for example, the day with relative
    value -1 is "Yesterday"). Where there is not a convenient, customary
    word or phrase in a particular language for a relative value, it
    should be omitted.</p>
  </blockquote>
  
  <p>how to use it in Xcode?</p>