SQL & PL/SQL

Hi all,

I need to find the number of weeks for a given year as it can be 52 or 53 when using ISO (IW)

I thought of asking the week number for dec 31st but for 2019 that returns iso week 1 (of iso year 2020) :

select to_number(to_char(to_date('31/12/2019', 'DD/MM/YYYY'), 'IW')) a
from dual;

this returns 1 and doesn't help me

any ideas