wp_query (or hook) posts by date (id) in array then set post_type

Thank to @pietergoosen for “jokingly” giving me the answer.

 function gm_gather_posts_in_array() {
    $set_days_before="1275";
    $posts_to_be_processed = date('Y-m-d', strtotime("today - $set_days_before days"));
    $args = array( 
            'post_type'      => 'post',
            'post_status'    => 'publish',
            'orderby'        => 'date',
            'order'          => 'DESC',
            'posts_per_page' => -1,
            'fields'         => 'ids',
            'date_query'     => array(
                            array(
                                'before' => $posts_to_be_processed
                            )
                    )
            );
    $posts_to_be_processed = new WP_Query( $args );

    return $posts_to_be_processed;

    }


function gm_update_posts_to_be_archived() {
        $posts_ready_to_be_processed = gm_gather_posts_in_array();
             if ( $posts_ready_to_be_processed->have_posts() ) {
                while ( $posts_ready_to_be_processed->have_posts() ) {
                    $posts_ready_to_be_processed->the_post();
                        $process_post = array(
                        'ID'           => get_the_id(),
                        'post_type'   => 'custom_post_type',
                        );

                        wp_update_post( $process_post ); 

                    }

                }


            wp_reset_postdata();
}

   echo gm_update_posts_to_be_processed();