Oracle 18c

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ALTER SESSION SET NLS_DATE_FORMAT = 'YYYY-MM-DD HH24:MI:SS'
CREATE TABLE table_name ( start_date DATE )
INSERT INTO table_name ( start_date )
SELECT DATE '2021-06-13' + INTERVAL '00:00:00' HOUR TO SECOND FROM DUAL UNION ALL
SELECT DATE '2021-06-13' + (SYSDATE - TRUNC(SYSDATE)) FROM DUAL UNION ALL
SELECT DATE '2021-06-13' + (SYSDATE - TRUNC(SYSDATE)) + INTERVAL '1' SECOND FROM DUAL UNION ALL
SELECT DATE '2021-06-13' + INTERVAL '23:59:59' HOUR TO SECOND FROM DUAL;
4 rows affected

SELECT *
FROM   table_name
WHERE  start_date >= DATE '2021-01-01'
AND    start_date <  TRUNC( SYSDATE, 'IW' )


START_DATE


2021-06-13 00:00:00

2021-06-13 19:48:47

2021-06-13 19:48:48

2021-06-13 23:59:59


SELECT *
FROM   table_name
WHERE  start_date >= TRUNC( SYSDATE, 'YYYY' )
AND    start_date <  TRUNC( SYSDATE, 'IW' )