Flutter check if DateTime actually exists

In my app the user can add a DateTime. For that I am not using a simple DatePicker but instead something custom, where I get two Strings for each Day & Month (dd, mm). My problem right now is that I need to validate this input. And I tried a couple of things but couldn't get a good working solution!

  DateTime getDateTime(BuildContext context) {
    return DateTime(2021, (m1! * 10 + m2!), (d1! * 10 + d2!));
  }

This is what Ive tried. The problem is that the user can also give me anything (any int) for m1, m2, d1 and d2 and DateTime simply formats that in a regular DateTime.

Is there a way to check if a given DateTime in the past existed?

German format

01.05. -> true

00.05. -> false

51.05. -> false

31.02. -> false

15.10. > true

I implemented by using 'parseStrict' method in DateFormat.

The 'parseStrict' throw exception does not match real date.

bool isValidDate({y = 2021, m1, m2, d1, d2}) {
    DateFormat format = DateFormat('yyyy/M/d');
    try {
      String md = '$y/${m1 * 10 + m2}/${d1 * 10 + d2}';
      format.parseStrict(md);
      return true;
    } catch (error) {
      return false;
    }
}

Usage

isValidDate(m1: 1, m2: 1, d1: 3, d2: 0);