Publishdate shows wrong date

Hi,

I have an integration where posts from that site saves as a post in wordpress, but I can’t seem to figure out how to get the ‘post_date’ to show the actual PublishDate.. It saves and are shown with the date ‘1970-01-01’, but if I print out $item->PublishDate I get the real date..
Could someone please help me figure this out?

function fetch_cision_news()
    {
        $params = array(
            'PageIndex' => 1,
            'PageSize' => 0,
            'detailLevel' => 'detail',
            'format' => 'json',
            'tags' => null,
            'startDate' => null,
            'endDate' => null,
        );
        $url = self::CISION_BLOCK_FEED_URL . self::CISION_SOURCE_UID . '?' . http_build_query($params);
        $response = wp_safe_remote_request($url, array(
            'headers' => array(
                'User-Agent' => 'mbp/cision',
            ),
        ));
        $result = null;
        if (!is_wp_error($response) && ($response['response']['code'] == 200 || $response['response']['code'] == 201)) {
            $result = json_decode( $response['body'] );
            if ( isset( $result->Releases ) && is_array( $result->Releases ) ) {
                foreach ( $result->Releases as $item ) {
                    $post_list = get_posts( array(
                        'cat' => self::WP_CATEGORY,
                        'meta_key' => 'cision_item_id',
                        'meta_value' => $item->EncryptedId,
                        'post_type' => 'post',
                    ) );

                    if (empty($post_list)) {
                        $postarr = array(
                            'comment_status' => 'closed',
                            'meta_input' => array(
                                'cision_item_id' => $item->EncryptedId,
                                'is_regulatory' => (int) $item->IsRegulatory,
                            ),
                            'ping_status' => 'closed',
                            'post_category' => array( self::WP_CATEGORY ),
                            'post_status' => 'publish',
                            'post_author' => 1,
                            'post_content' => $item->Body,
                            'post_date' => date( 'Y-m-d H:i:s', $item->PublishDate ),
                            'post_date_gmt' => date( 'Y-m-d H:i:s', $item->PublishDate ),
                            'post_title' => $item->Title,
                            'post_type' => 'post',
                            'posts_per_page' => 1,
                        );
                        wp_insert_post( $postarr, false );
                    }
                }
            }
        }