Week number giving 1 week less number

Hi team,
I am getting 1 week less when running the query to check.Below is my test.Current week no is 21 but it is showing 20.

vertdba=> SELECT CURRENT_TIMESTAMP
vertdba-> ;

?column?

2020-05-19 03:43:39.792345-05
(1 row)
vertdba=> select TO_CHAR( CURRENT_TIMESTAMP AT TIMEZONE 'UTC'::DATE - INTERVAL '0 WEEKS','YYYYWW')::INT;

TO_CHAR

202020
(1 row)
vertdba=> select week(current_timestamp);

week

21
(1 row)

But what wrong in the below query which is giving week 20.
vertdba=> SELECT TO_CHAR( CURRENT_TIMESTAMP AT TIMEZONE 'UTC'::DATE - (0::varchar(6) || ' WEEKS')::interval,'YYYYWW')::INT;

TO_CHAR

202020
(1 row)