Get More friendly remaining time from date and time string in flutter

remaining_time.dart

String getRemainingTime(String? deadline) {
  String toRet = "";
  int remSecs = secondsBetween(DateTime.now(), DateTime.parse(deadline!));
  if (remSecs < 0) {
    isUrgent=true;
    toRet = "Overdue by ";
    remSecs = remSecs * -1;
  }
  int mdays = (remSecs / 86400).truncate();
  int rdays = (remSecs % 86400).truncate();
  int mhrs = 0;
  int rhrs = 0;
  int mmins = 0;
  int rmins = 0;
  int msec = 0;
  if (mdays > 0) {
    mhrs = (rdays / 3600).truncate();
    rhrs = (rdays % 3600).truncate();

    Timer.periodic(const Duration(hours: 1), (Timer t) {
      if (mounted) setState(() {});
    });
    toRet = "$toRet $mdays days $mhrs hrs";
  } else {
    mhrs = (rdays / 3600).truncate();
    rhrs = (rdays % 3600).truncate();
    if (mhrs > 0) {
      mmins = (rhrs / 60).truncate();
      rmins = (rhrs % 60).truncate();

      toRet = "$toRet $mhrs hrs $mmins mins";
      Timer.periodic(const Duration(minutes: 1), (Timer t) {
        if (mounted) setState(() {});
      });
    } else {
      mmins = (rhrs / 60).truncate();
      rmins = (rhrs % 60).truncate();
      msec = (rmins / 60).truncate();

      toRet = "$toRet $mmins mins $rmins secs";
      Timer.periodic(const Duration(seconds: 1), (Timer t) {
        if (mounted) setState(() {
          isUrgent=true;
        });
      });
    }
  }

  return toRet;
}
  int secondsBetween(DateTime from, DateTime to) {
    // from = DateTime(from.year, from.month, from.day);
    // to = DateTime(to.year, to.month, to.day);
    return (to.difference(from).inSeconds).round();
  }

the deadline tested had the format YYYY-MM-dd HH:mm:ss