title: IOS: problem with NSDate
body: <p>I have this code:</p>
  
  <pre><code>NSDateComponents *components = [[[NSDateComponents alloc] init] autorelease];
  [components setYear:2011];
  [components setDay:1];
  [components setMonth:4];
  NSCalendar *gregorianCalendar = [[[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar] autorelease];
  NSDate *firstDate = [gregorianCalendar dateFromComponents:components];
  NSLog(@"date:%@", firstDate);
  </code></pre>
  
  <p>the result in console is:</p>
  
  <pre><code>date:2011-03-31
  </code></pre>
  
  <p>why???? if I set "setDay:1" it would be "date:2011-04-01", no?</p>