Given a sysdate = Sep 13, 2018 13:14:15,
sysdate = Sep 13, 2018 13:14:15
How do we get/extract that it is 256th day of the year / 257th in leap year from dual?
You could use this:
SELECT TO_CHAR(sysdate, 'DDD') FROM dual;
Refer to docs_Format_Models for more informations.