title: How does one subtract hours from an NSDate?
body: <p>I would like to subtract 4 hours from a date. I read the date string into an NSDate object use the following code:</p>
  
  <pre><code>NSDateFormatter * dateFormatter = [[[NSDateFormatter alloc] init] autorelease];
  [dateFormatter setDateFormat:@"yyyy-MM-dd'T'HH:mm:ssZ"];
  NSDate * mydate = [dateFormatter dateFromString:[dict objectForKey:@"published"]];
  </code></pre>
  
  <p>What do I do next?</p>