How to write a function to find weekday

Question

my code as follow:
create or replace function getweekday(arg_day_IN VARCHAR2)
RETURN varchar2
IS
arg_day VARCHAR2(8) := arg_day_IN;
ls_week VARCHAR2(1);
ls_week_name VARCHAR2(4);
ls_date_1 date;
BEGIN
ls_date_1 := to_char(SUBSTR(arg_day, 5, 2) || '-' || SUBSTR(arg_day, 7, 2) )|| '-' ||SUBSTR(arg_day, 1, 4));
ls_week := OMWB_emulation.utilities.WEEKDAY(ls_date_1);
RETURN ls_week;
END getweekday;
There is a problem that when i execute this function it returns a error code ora-01843, it shows that it is not a valid month.
How can I know what is a valid month format? How to find the correct month format?
Which one is the valid date format- 02-01-2004 or 02-Jan-2004 or 02-January-2004.
Please help me to solve this problem. Thanks a lot.

Answer 1

If the input parameter format is 'yyyymmdd' you can do:
create or replace function getweekday(arg_day_IN VARCHAR2)
RETURN varchar2
IS
ls_week VARCHAR2(1);
BEGIN
ls_week := to_char(to_date(agr_day_IN,'yyyymmdd'),'D');
RETURN ls_week;
END getweekday;