code: private void checkDates() {
  		DateTime created = this.dateCreated;
  		DateTime published = this.datePublished;
  		DateTime modified = this.dateModified;
  		DateTime reviewed = this.dateReviewed;
  		if(
  			created != null
  			&& published != null
  			&& published.compareTo(created) < 0
  		) throw new IllegalArgumentException("published may not be before created");
  		if(
  			created != null
  			&& modified != null
  			&& modified.compareTo(created) < 0
  		) throw new IllegalArgumentException("modified may not be before created");
  		if(
  			created != null
  			&& reviewed != null
  			&& reviewed.compareTo(created) < 0
  		) throw new IllegalArgumentException("reviewed may not be before created");
  	}
docs: Checks the dates for consistency.