@Override
	public int compare(Drillable one, Drillable two) {
		if (one.getLastEdited() == null && two.getLastEdited() == null) {
			return 0;
		}
		if (one.getLastEdited() == null) {
			return -1;
		}
		if (two.getLastEdited() == null) {
			return 1;
		}
		return one.getLastEdited().compareTo(two.getLastEdited());
	}