code: public boolean isDateAllowed(LocalDate date) {
          if (date == null) {
              return allowEmptyDates;
          }
          return (!(InternalUtilities.isDateVetoed(vetoPolicy, date)));
      }
docs: isDateAllowed, This checks to see if the specified date is allowed by any currently set veto
  policy, and allowed by the current setting of allowEmptyDates.
  
  If allowEmptyDates is false, and the specified date is null, then this returns false.
  
  If a veto policy exists, and the specified date is vetoed, then this returns false.
  
  If the date is not vetoed, or if empty dates are allowed and the date is null, then this
  returns true.