code: public boolean isValidDate(int year) {
  
          return (
              (year >= GregorianMath.MIN_YEAR) && (year <= GregorianMath.MAX_YEAR)
              && ((this.month != 2) || (this.dayOfMonth != 29) || GregorianMath.isLeapYear(year))
          );
  
      }
docs: /*[deutsch]
  <p>Pr&uuml;ft, ob diese Instanz zum angegebenen gregorianischen Jahr ein g&uuml;ltiges
  ISO-Kalenderdatum ergibt. </p>
  
  @param   year        proleptic iso year [(-999,999,999)-999,999,999]
  @return  {@code true} if the year argument is out of range or if this instance represents
  the 29th of February and is not valid for given year else {@code false}
  @see     #atYear(int)