Oracle 11g Release 2

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-- should be 2012
SELECT   (EXTRACT (YEAR FROM ADD_MONTHS (DATE '2013-09-30', -9))||'-10-01') from dual;

(EXTRACT(YEARFROMADD_MONTHS(DATE'2013-09-30',-9))||'-10-01')

2012-10-01

-- should be 2013
SELECT   (EXTRACT (YEAR FROM ADD_MONTHS (DATE '2013-10-01', -9))||'-10-01') from dual;

(EXTRACT(YEARFROMADD_MONTHS(DATE'2013-10-01',-9))||'-10-01')

2013-10-01

-- should be 2018
SELECT   (EXTRACT (YEAR FROM ADD_MONTHS (SYSDATE, -9))||'-10-01') from dual;

(EXTRACT(YEARFROMADD_MONTHS(SYSDATE,-9))||'-10-01')

2022-10-01