title: Difference between arrival and departure
body: <pre><code>departure_day        departure_time            arrival_day        arrival_time  
  1                    00:00:00                  3                  01:00:00   
  1                    10:00:00                  1                  02:00:00   
  6                    15:00:00                  1                  06:00:00  
  </code></pre>
  
  <p>I would like to have a variable that has the difference between those two. 1 is for Monday and 7 for Sunday. Additionally, sometimes it goes from 6 to 1 for example like the last case. </p>
  
  <p>I would like to convert it to hours and days in the end. 
  So far I have transformed them also to DateTime variables but I am struggling at the moment. Any tips on how to move forward? </p>
  
  <pre><code>Example output:
  difference (in hours)
  49
  14
  39
  </code></pre>