code: public DateDue setDateDue(Date dateDue, boolean hasTime) {
  		DateDue prop = (dateDue == null) ? null : new DateDue(dateDue, hasTime);
  		setDateDue(prop);
  		return prop;
  	}
docs: Sets the date that a to-do task is due by. This must NOT be set if a
  {@link DurationProperty} is defined.
  @param dateDue the due date or null to remove
  @param hasTime true if the date has a time component, false if it is
  strictly a date (if false, the given Date object should be created by a
  {@link java.util.Calendar Calendar} object that uses the JVM's default
  timezone)
  @return the property that was created
  @see <a href="http://tools.ietf.org/html/rfc5545#page-96">RFC 5545
  p.96-7</a>
  @see <a href="http://tools.ietf.org/html/rfc2445#page-92">RFC 2445
  p.92-3</a>
  @see <a href="http://www.imc.org/pdi/vcal-10.doc">vCal 1.0 p.30</a>