title: iPhone SDK - NSDateFormatter - NSDate from string always returns nil
body: <p>So this sounds like it should be so simple, yet for me, this code block returns a <code>nil</code> date:</p>
  
  <pre><code>NSDateFormatter *df = [[NSDateFormatter alloc] init];
  [df setDateFormat:@"yyyy-MM-dd hh:mm:ss"];
  NSDate *newStartDate = [df dateFromString:@"2012-05-11 20:45:00"];
  </code></pre>
  
  <p>Does anyone have any idea what could be causing <code>newStartDate</code> to be returned as <code>nil</code>? <code>df</code> is valid, the format string appears to be valid. I'm completely stuck here, so any advice would be great!</p>
  
  <p>Thanks!</p>