Use the MONTHS_BETWEEN function : MONTHS_BETWEEN « Date Timestamp Functions « Oracle PL/SQL Tutorial

1. Oracle PL/SQL Tutorial
2. Date Timestamp Functions
3. MONTHS_BETWEEN

To find the time difference between two dates, use the MONTHS_BETWEEN function.

The MONTHS_BETWEEN function returns fractional months.

The general format of the function is: MONTHS_BETWEEN(date1, date2)

where the result will be date1 - date2.

SQL>
SQL> SELECT MONTHS_BETWEEN(TO_DATE('22SEP2006','ddMONyyyy'), TO_DATE('13OCT2001','ddMONyyyy')) "Months difference"
  2  FROM dual;

Months difference
-----------------
       59.2903226

SQL>