Oracle 21c

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CREATE OR REPLACE FUNCTION random_timestamp(
  p_from      IN TIMESTAMP,
  p_to        IN TIMESTAMP,
  p_fraction  IN VARCHAR2   DEFAULT 'Y'
) RETURN TIMESTAMP
IS
  return_val_y TIMESTAMP(9) := p_from + dbms_random.value() * (p_to - p_from);
  return_val_n TIMESTAMP(0) := return_val_y;
BEGIN
  RETURN CASE
         WHEN p_fraction LIKE 'Y%' OR p_fraction LIKE 'y%'
         THEN return_val_y
         ELSE return_val_n
         END;
END random_timestamp;
/
SELECT * FROM USER_ERRORS;
SELECT MIN(ts),
       MAX(ts)
FROM   (
  SELECT random_timestamp(
           TIMESTAMP '2023-01-25 09:00:00',
           TIMESTAMP '2023-01-25 12:00:00'
         ) AS ts
  FROM   DUAL
  CONNECT BY LEVEL <= 1e6
);


MIN(TS)
MAX(TS)


25-JAN-23 09.00.00.017186000
25-JAN-23 11.59.59.999534000