if (this.minute != FIRST_MINUTE_IN_HOUR) {
            result = new Minute(this.minute - 1, getHour());
        }
        else {
            Hour h = (Hour) getHour().previous();
            if (h != null) {
                result = new Minute(LAST_MINUTE_IN_HOUR, h);
            }
            else {
                result = null;