For running J!5.1 you must https://fabrikar.com/forums/index.php?wiki/update-from-github/ or include the new file manually https://fabrikar.com/forums/index.php?threads/joomla-5-1-and-fabrik-cannot-find-files-error.54473/post-285151 See also Announcements
Please see our announcement here.
// get the time1 value, 'explode' it into an array, and calculate the total seconds
$time1_raw = '{yourtable___time1_raw}';
$time1 = explode(':', $time1_raw);
$seconds1 = ($time1[0] * 60 * 60) + ($time1[1] * 60) + ($time1[2]);
// do the same for time2
$time2_raw = '{yourtable___time2_raw}';
$time2 = explode(':', $time2_raw);
$seconds2 = ($time2[0] * 60 * 60) + ($time2[1] * 60) + ($time2[2]);
// return the difference
return $seconds2 - $seconds1;