(let* ((elapsed
        (float-time
         (time-subtract
          (date-to-time "2019-01-17 18:05")
          (date-to-time "2019-01-17 13:19"))))
       (in_minutes (/ elapsed 60))
       (in_hours (/ in_minutes 60))
       (remained_minutes (mod in_minutes 60)))
  (format "%d hours %d minutes" in_hours remained_minutes))