История изменений

    var birthDate = LocalDate.of(2000, AUGUST, 24);
    var periodFrom = LocalDate.of(2010, JANUARY, 1);
    var periodTo = LocalDate.of(2020, JANUARY, 1);


    var result = 0;

    var age = 0;
    while (true) {
      var date = birthDate.plusYears(age);
      if (date.isAfter(periodTo)) {
        break;
      }
      if (!date.isBefore(periodFrom)) {
        result++;
      }
      age++;
    }

    out.println(result);