code: public void register(Date date) {
  		if(date != null) {
  			if(first == null) {
  				// initialization
  				first = date;
  				last = date;
  			} else if(date.before(first)) {
  				first = date;
  			} else if(date.after(last)) {
  				last = date;
  			}
  		}
  	}
docs: Registers the given date. The timestamp boundaries will be
  potentially adjusted to accomodate for inclusion of this date.
  
  @param date Date to be registered.