title: Substract two QString
body: <p>I´m trying to substract two hours.</p>
  
  <pre><code>QString 1 = "11:00";
  QString 2 = "10:00";
  </code></pre>
  
  <p>I would like to save the result from (11:00 - 10:00) into another QString.</p>
  
  <p>Does anyone know how could I do this?</p>
  
  <p>Thanks for replying!</p>