Oracle 21c

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ALTER SESSION SET NLS_DATE_FORMAT = 'YYYY-MM-DD HH24:MI:SS';
ALTER SESSION SET NLS_TIMESTAMP_FORMAT = 'YYYY-MM-DD HH24:MI:SS.FF'
ALTER SESSION SET NLS_TIMESTAMP_TZ_FORMAT = 'YYYY-MM-DD HH24:MI:SS.FF TZR'
SELECT SYSTIMESTAMP, TRUNC(SYSTIMESTAMP) FROM DUAL;

SYSTIMESTAMP
TRUNC(SYSTIMESTAMP)

2024-02-28 19:14:23.531132 +00:00
2024-02-28 00:00:00

SELECT SYSTIMESTAMP, TO_CHAR(SYSTIMESTAMP, 'YYYY-MM-DD') FROM DUAL;

SYSTIMESTAMP
TO_CHAR(SYSTIMESTAMP,'YYYY-MM-DD')

2024-02-28 19:14:23.533246 +00:00
2024-02-28