안녕하세요.

아래 쿼리를 실행하면 
ORA-01840: 입력된 값의 길이가 날짜 형식에 비해 부족합니다
라고 나오는데 어디가 문제인지 모르겠습니다.
and a.age >= 7를 빼면 조회가 되는데
이걸 넣으면 날짜 형식 오류가 나는데 months_between 리턴값은 숫자 아닌가요?
뭐가 문제인지...
도와주세요...

SELECT DEPTCODE, EMPNO, EMPNAME, ENTERDATE,
       WORK_YEAR, WORK_MONTH,
       FAMILYNAME, RELATIONCODE, RESIDENTNO1, AGE,
       CASE 
            WHEN AGE BETWEEN 20 AND 27 THEN 'University'
            WHEN AGE BETWEEN 17 AND 19 THEN 'high school'
            WHEN AGE BETWEEN 14 AND 16 THEN 'middle School'
            WHEN AGE BETWEEN 8  AND 13 THEN 'elementary'
            ELSE 'Preschool'
       END AS SCHOOL
FROM
(
SELECT T1.DEPTCODE, T1.EMPNO, T1.EMPNAME, T1.ENTERDATE,
       FUN_CALC_YEARS_CNT(ENTERDATE,TO_CHAR(SYSDATE, 'yyyymmdd'), 'Y') WORK_YEAR,
       FUN_CALC_YEARS_CNT(ENTERDATE,TO_CHAR(SYSDATE, 'yyyymmdd'), 'M') WORK_MONTH,
       T2.FAMILYNAME, T2.RELATIONCODE,
       CRYPTSTRING.DECRYPT(T2.RESIDENTNO1,'BDS3018508125')AS RESIDENTNO1,
       CRYPTSTRING.DECRYPT(T2.RESIDENTNO2,'BDS3018508125')AS RESIDENTNO2,
       months_BETWEEN(TRUNC(SYSDATE,'YEAR'), 
       TRUNC(TO_DATE( CASE
                      WHEN SUBSTR( CRYPTSTRING.DECRYPT(T2.RESIDENTNO2,'BDS3018508125'), 1, 1) IN ('1','2','5','6')  THEN '19'||CRYPTSTRING.DECRYPT(T2.RESIDENTNO1,'BDS3018508125')
                      WHEN SUBSTR( CRYPTSTRING.DECRYPT(T2.RESIDENTNO2,'BDS3018508125'), 1, 1) IN ('3','4','7','8')  THEN '20'||CRYPTSTRING.DECRYPT(T2.RESIDENTNO1,'BDS3018508125')
                      END,'YYYYMMDD'),'YEAR')) / 12 + 1 AS AGE
FROM P1_MASTER T1, P1_FAMILIES T2
WHERE T1.EMPNO = T2.EMPNO(+)
and SERVICEKINDCODE  = '1'
AND T2.SCHOOLGUBN = '2'
) A
where a.work_year >= 1
and a.age >= 7