if (o1 instanceof Month) {
            Month m = (Month) o1;
            result = this.year - m.getYearValue();
            if (result == 0) {
                result = this.month - m.getMonth();
            }
        }

        // CASE 2 : Comparing to another TimePeriod object
        // -----------------------------------------------
        else if (o1 instanceof RegularTimePeriod) {
            // more difficult case - evaluate later...
            result = 0;
        }

        // CASE 3 : Comparing to a non-TimePeriod object
        // ---------------------------------------------
        else {
            // consider time periods to be ordered after general objects
            result = 1;