DECLARE
    CURSOR V_CUR
      IS
        SELECT  TABLE_OWNER,
                TABLE_NAME,
                PARTITION_NAME,
                HIGH_VALUE
          FROM  DBA_TAB_PARTITIONS
          WHERE TABLE_OWNER = '&TABLE_OWNER'
            AND TABLE_NAME = '&TABLE_NAME';
    V_HIGH_VALUE DATE;
BEGIN
    FOR V_REC IN V_CUR LOOP
      EXECUTE IMMEDIATE 'SELECT ' || V_REC.HIGH_VALUE || ' FROM DUAL'
        INTO V_HIGH_VALUE;
      DBMS_OUTPUT.PUT_LINE(RPAD(V_REC.PARTITION_NAME,31) || TO_CHAR(V_HIGH_VALUE,'YYYY/MM/DD HH24:MI:SS'));
    END LOOP;
END;
/

SELECT  TABLE_OWNER,
        TABLE_NAME,
        PARTITION_NAME
  FROM  DBA_TAB_PARTITIONS
  WHERE TABLE_OWNER = '&TABLE_OWNER'
    AND TABLE_NAME = '&TABLE_NAME'
    AND PARTITION_NAME < TO_CHAR(ADD_MONTHS(TRUNC(SYSDATE,'MM'),-3),'"P_"YYYYMM')
/