Diferença entre durations em Dart

main.dart

void main() {
  Duration duration = Duration(minutes: 1, seconds: 10);
  int d1 = duration.inMicroseconds;  
  Duration duration2 = Duration(minutes: 2, seconds: 25);
  int d2 = duration2.inMicroseconds;
  print('$duration -> $d1');
  print('$duration2 -> $d2');
  int diff = d2-d1;
  Duration duration3 = Duration(microseconds: diff);
  print('$duration3 -> $diff');
  print(duration2 - duration);
}