title: LibreOffice SUM time period in format HH:MM:SS
body: <p>I want to obtain the sum of several cells containing a period of time in the format HH:MM:SS.
  In LibreOffice Calc 4.0.3.3, I've copy-pasted the periods of time in the range G14:G21, and formatted the cells as Time HH:MM:SS.
  I formatted in the same way the cell G22, and inserted in it the following SUM function:</p>
  
  <pre><code>=SUM(G14:G21)
  </code></pre>
  
  <p>Instead of the expected result, the function returns me this solution 00:00:00.
  Could you explain me where am I wrong?</p>