getDatesByDay method
Implementation
List<DateTime> getDatesByDay(int year, int month, String day) {
Year y = years!.firstWhere((element) => element.value == year);
Month m = y.months.firstWhere((element) => element.value == month);
List<Day> d = m.days.where((element) => element.name.toLowerCase() == day.toLowerCase()).toList();
return d.map((e) => DateTime(year, month, e.value)).toList();
}