Oracle 18c

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ALTER SESSION SET NLS_DATE_FORMAT='YYYY-MM-DD HH24:MI:SS';
CREATE TABLE test_data ( start_date, end_date ) AS
  SELECT DATE '2019-07-01',
         DATE '2020-07-01' + INTERVAL '15:30:00' HOUR TO SECOND
  FROM   DUAL
UNION ALL
  SELECT DATE '2019-07-31',
         DATE '2020-02-29' + INTERVAL '15:30:00' HOUR TO SECOND
  FROM   DUAL
UNION ALL
  SELECT DATE '2019-02-28',
         DATE '2020-02-29' + INTERVAL '15:30:00' HOUR TO SECOND
  FROM   DUAL;
3 rows affected

SELECT start_date,
       end_date,
       CEIL(
         (
         MONTHS_BETWEEN( end_date, start_date )
         +
         CASE
         WHEN EXTRACT( DAY FROM start_date ) = EXTRACT( DAY FROM end_date )
         OR   ( start_date = LAST_DAY( start_date ) AND end_date = LAST_DAY( end_date ) )
         THEN ( end_date
                - ADD_MONTHS( start_date, MONTHS_BETWEEN( end_date, start_date ) )
              ) / 31
         ELSE 0
         END
         )
         / 12
       ) AS years
FROM   test_data;


START_DATE
END_DATE
YEARS


2019-07-01 00:00:00
2020-07-01 15:30:00
2

2019-07-31 00:00:00
2020-02-29 15:30:00
1

2019-02-28 00:00:00
2020-02-29 15:30:00
2

START_DATE	END_DATE	YEARS
2019-07-01 00:00:00	2020-07-01 15:30:00	2
2019-07-31 00:00:00	2020-02-29 15:30:00	1
2019-02-28 00:00:00	2020-02-29 15:30:00	2