calculate method

String calculate(DateTime date1, DateTime date2)

String method calculate takes date1 and date2 and return String value Date Difference

Implementation

String calculate(DateTime date1, DateTime date2) {
  var oldDate = date1.isBefore(date2) ? date1 : date2;
  var newDate = date1.isAfter(date2) ? date1 : date2;
  newDate = newDate.add(const Duration(seconds: 1));
  var diff = date2.difference(date1).abs();

  int yearCount = 0,
      monthCount = 0,
      dayCount = 0,
      hourCount = 0,
      minuteCount = 0;

  if (diff.inDays < 28) {
    dayCount = diff.inDays;
    hourCount = diff.inHours % 24;
    minuteCount = diff.inMinutes % 60;
  } else {
    while (true) {
      if (DateTime(oldDate.year + 1, oldDate.month, oldDate.day)
          .isBefore(newDate)) {
        oldDate = DateTime(oldDate.year + 1, oldDate.month, oldDate.day);
        yearCount++;
      } else if ((oldDate.month == 12
              ? DateTime(oldDate.year + 1, 1, oldDate.day)
              : DateTime(oldDate.year, oldDate.month + 1, oldDate.day))
          .isBefore(newDate)) {
        oldDate = oldDate.month == 12
            ? DateTime(oldDate.year + 1, 1, oldDate.day)
            : DateTime(oldDate.year, oldDate.month + 1, oldDate.day);
        monthCount++;
      } else {
        if (FlutterDateDifferenceHelper.getDayCountInMonth(
                oldDate.year, oldDate.month) <
            oldDate.day + 1) {
          if ((oldDate.month + monthCount == 12
                  ? DateTime(oldDate.year + 1, 1, 1)
                  : DateTime(oldDate.year, oldDate.month + 1, 1))
              .isBefore(newDate)) {
            oldDate = oldDate.month + monthCount == 12
                ? DateTime(oldDate.year + 1, 1, 1)
                : DateTime(oldDate.year, oldDate.month + 1, 1);
            dayCount++;
          } else {
            break;
          }
        } else if (DateTime(oldDate.year, oldDate.month, oldDate.day + 1)
            .isBefore(newDate)) {
          oldDate = DateTime(oldDate.year, oldDate.month, oldDate.day + 1);
          dayCount++;
        } else {
          break;
        }
      }
    }
  }

  return FlutterDateDifferenceHelper.countsToString(
      yearCount, monthCount, dayCount, hourCount, minuteCount);
}