title: NSDateFormatter with default time zone gives different date than NSDate description method
body: <pre><code>NSDate *date = [NSDate dateWithTimeIntervalSince1970:timestamp];
  NSDateFormatter *_dateFormatter = [[NSDateFormatter alloc] init];
  [_dateFormatter setTimeZone:[NSTimeZone defaultTimeZone]];
  [_dateFormatter setDateFormat:@"dd-MM-yy HH:mm"];
  NSString *dateString = [_dateFormatter stringFromDate:date];
  NSLog(@"Date: %@ formatted: %@", date, dateString);
  [_dateFormatter release];
  </code></pre>
  
  <p>Gives me wrong date formatted: </p>
  
  <p><strong>Date: 2013-01-31 18:00:00 +0000 formatted: 31-01-13 19:00 (from timestamp: 1359655200.000000)</strong></p>
  
  <p>Online conversion tool: <a href="http://www.onlineconversion.com/unix_time.htm">http://www.onlineconversion.com/unix_time.htm</a> indicates that 1st date is correct: 2013-01-31 18:00:00 +0000.</p>
  
  <p>Why NSDateFormatter produces different date that NSLog? Shouldn't <code>[NSDate description]</code> use defaultTimeZone when printing to console? I get the same error with <code>[_dateFormatter setTimeZone:[NSTimeZone localTimeZone]]</code>; and <code>[_dateFormatter setTimeZone:[NSTimeZone systemTimeZone]]</code>;</p>