SQL> SELECT TO_CHAR(date '1982-03-09', 'DAY') day FROM dual;
DAY
---------
TUESDAY
SQL> SELECT TO_CHAR(date '1982-03-09', 'DY') day FROM dual;
DAY
---
TUE
SQL> SELECT TO_CHAR(date '1982-03-09', 'Dy') day FROM dual;
DAY
---
Tue
(Note that the queries use ANSI date literals, which follow the ISO-8601 date standard and avoid date format ambiguity.)