title: FastReport calculate hours from Date_From and Date_To fields
body: <p>I am using FastReport with Delphi. I have following fields:</p>
  
  <pre><code>DATE_FROM  (example: 01.05.2015.)
  TIME_FROM  (example: 13:00)
  
  DATE_TO    (example: 02.05.2015.)
  TIME_TO    (example: 10:00)
  </code></pre>
  
  <p>I need to calculate how many days and hours have passed between these pairs of dates. In this example it is less than 24 hours... so the result should be:</p>
  
  <pre><code>0 days   21 hours
  </code></pre>
  
  <p>How to achieve that?</p>