title: iOS setDateFormat bug with displaying hour
body: <p>I have a code like this:</p>
  
  <pre><code>[dateFormat setDateFormat:@"HH:mm"];
  dateHM = [dateFormat stringFromDate:date];
  </code></pre>
  
  <p>I use dateHM (<code>NSString</code>) in stringWithFormat:, and i expected to always have it displayed as for example 23:00, not 11:00. It works right almost every time, but some app users are getting 12-hours format with AM/PM added...</p>
  
  <p>How is that possible? Does global user preferences make a difference, or what?</p>