title: How to get a week number from NSDate consistently in all iOS versions?
body: <p>I use the following to obtain a week number from an NSDate:</p>
  
  <pre><code>[[calendar components: NSWeekCalendarUnit fromDate:date] week]
  </code></pre>
  
  <p>Unfortunately, I get different values in different iOS versions. Values returned by iOS 4.* and 5 differ by 1. Is there any way to retrieve week number consistently?</p>