I have a view which is built on a CTE.

create or replace view viewname
as
WITH all_dates AS 
(
SELECT generate_series
    (
        ( SELECT min(date_trunc('day'::text, problem_time))::date AS min 
            FROM tablename)
        , now()::date
        , '1 day'::interval
    )::date AS date_id
)
, ..... rest of view

When the command is executed, Postgres is generating the view as

create or replace viewname
as
WITH all_dates AS 
(
SELECT generate_series
    (
        (
            ( SELECT min(date_trunc('day'::text,problem_time))::date AS min
                   FROM tablename))::timestamp with time zone
            , now()::date::timestamp with time zone
            , '1 day'::interval)::date AS date_id
        )
, ..... rest of view

This continues further down the CTE structure when doing filters with timestamp fields, the value being compared to is converted to timestamptz.

Where I wrote

where response >= reference

-- response is a timestamp type
-- reference is a timestamp type from some other preceding query 

Postgres is converting to

where response >= reference::timestamp with time zone

My questions are why is this happening and how can I prevent it?