title: -[NSCalendar components:fromDate:toDate:options] always returns 0 diff
body: <p>I have read some threads on how to calc diff between 2 dates in iOS, here is an example which also seems to be provided by Apple docs, and I use it to decide if 2 dates are the same (ignoring the time). But the components: method always returns year=0, month=0, day=0, even if the 2 dates are different. I have no idea why... I'd appreciate your thought...</p>
  
  <pre><code>+ (BOOL)isSameDate:(NSDate*)d1 as:(NSDate*)d2 {
  if (d1 == d2) return true;
  if (d1 == nil || d2 == nil) return false;
  
  NSCalendar* currCal = [NSCalendar currentCalendar];
  
  // messing with the timezone - can also be removed, no effect whatsoever:
  NSTimeZone* tz = [NSTimeZone timeZoneForSecondsFromGMT:0];
  [currCal setTimeZone:tz];
  
  NSDateComponents* diffDateComps =
  [currCal components:NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit
          fromDate:d1 toDate:d2 options:0];
  
  return ([diffDateComps year] == 0 &amp;&amp; [diffDateComps month] == 0 &amp;&amp; [diffDateComps day] == 0);
  }
  </code></pre>