use java.time.Period

import java.time.LocalDate;
import java.time.Period;
public class Ch {
  public static void main(String[] args) {
    int a = 20200502; LocalDate la = lo(a); System.out.println(la);
    int b = 20190401; LocalDate lb = lo(b); System.out.println(lb);
    Period p = Period.between(lb, la);
    System.out.println(p);
    System.out.println(p.getYears());
    System.out.println(p.getMonths());
    System.out.println(p.getDays());
    System.out.println(la.minusYears(1).minusMonths(1).minusDays(1));
    System.out.println(la.minus(Period.parse("P1Y1M1D")));
  }
  private static LocalDate lo(int a) {
    return LocalDate.of(a / 10000, (a % 10000) / 100, a % 100);
  }
}