code: public DateUnit add() {
  		if (this.add.isPresent()) { return add.get(); }
  		
  		return (this.add = Optional.of((DateUnit) new DateUnit(this) {
  			
  			@Override protected DateUnit handle(int calendarField, int amount) {
  				Calendar c = asCalendar();
  				c.add(calendarField, amount);
  				target = c.getTime();
  		        return this;
  			}
  
  		})).get();
  	}
docs: Returns a AddsOrSets instance that add the specified field to a delegate date
  
  @return