PHP: Timestamp difference incorrect

The situation

I've got two timestamps.

One with the start time and one with the end time.

The start time is: 04:43:37
The end time is: 11:59:59

Now I am trying to get the difference between the dates like this:

//define timestamps
$start_time     = 1297698217;
$end_time      = 1297724399;
$time_diff    = $end_time - $start_time;

//display times and difference
echo 
    '<b>Start time:</b> ' . date('d-m-Y h:i:s', $start_time) . '<br />' .
    '<b>End time:</b> ' . date('d-m-Y h:i:s', $end_time) . '<br />' .
    '<b>Time difference::</b> ' . date('h:i:s', $time_diff);Copy code

The result

Start time: 14-02-2011 04:43:37
End time: 14-02-2011 11:59:59
Time difference: 08:16:22Copy code

The problem

Now the problem is that the result should be 07:16:22. I've tried this with different times, but every time I'm getting the same result. One hour too much difference.

Is there an expert willing to help?