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>