Oracle 18c

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.

ALTER SESSION SET NLS_DATE_FORMAT = 'YYYY-MM-DD HH24:MI:SS';
CREATE TABLE genmst_customer (id, dat_of_birth) AS
SELECT 1, DATE '1970-01-01' FROM DUAL UNION ALL
SELECT 2, DATE '1980-01-01' FROM DUAL UNION ALL
SELECT 3, DATE '1990-01-01' FROM DUAL UNION ALL
SELECT 4, DATE '2000-01-01' FROM DUAL;
4 rows affected

DECLARE
  v_date_of_birth GENMST_CUSTOMER.DAT_OF_BIRTH%TYPE;
BEGIN
  SELECT dat_of_birth
  INTO   v_date_of_birth
  FROM   genmst_customer
  WHERE  id = 1;

  DBMS_OUTPUT.PUT_LINE(TO_CHAR(v_date_of_birth, 'dd/mm/yyyy'));
END;
/
1 rows affected

dbms_output:
01/01/1970