long minutesBetween = ChronoUnit.MINUTES.between(l1,l2);
пример
LocalTime localTime=LocalTime.now();
LocalTime localTimeAfter5Minutes=LocalTime.now().plusMinutes(5);
Long minutesBetween=ChronoUnit.MINUTES.between(localTime,localTimeAfter5Minutes);
System.out.println("Diffrence between time in munutes : "+minutesBetween);