code: private DateValue generateInstance() {
  		try {
  			do {
  				if (!instanceGenerator.generate(builder)) {
  					return null;
  				}
  				DateValue dUtc = dtStart instanceof TimeValue ? TimeUtils.toUtc(builder.toDateTime(), tzid) : builder.toDate();
  				if (dUtc.compareTo(lastUtc_) > 0) {
  					return dUtc;
  				}
  			} while (true);
  		} catch (Generator.IteratorShortCircuitingException ex) {
  			return null;
  		}
  	}
docs: Generates a date.
  @return a date value in UTC or null if a date value could not be
  generated