title: NSDateFormatter too slow in Time profiler
body: <p>Time profiler say that my code to expressive in memory and I see lags while scrolling tableView.</p>
  
  <p>How can I replace this code?</p>
  
  <pre><code>NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
  [dateFormatter setDateFormat:@"mm:ss"];
  NSDate *date = [NSDate dateWithTimeIntervalSince1970:[_duration doubleValue]];
  return [dateFormatter stringFromDate:date];
  </code></pre>
  
  <p>_duration have value 123</p>
  
  <p>I need string from _duration like 2:03 sec</p>