gistfile1.txt

function remove_just_listed_flag() {
    $args = array(
        'post_type'      => 'property',
        'posts_per_page' => -1,
        'post_status'    => 'publish',
        'tax_query'      => array(
            array(
                'taxonomy' => 'marketing_flag',
                'field'    => 'slug',
                'terms'    => 'just-listed',
            ),
        ),
        'date_query'     => array(
            array(
                'column' => 'post_date_gmt',
                'before' => '1 month ago',
            ),
        ),
    );

    $query = new WP_Query($args);

    if ($query->have_posts()) {
        while ($query->have_posts()) {
            $query->the_post();
            $post_id = get_the_ID();
            wp_remove_object_terms($post_id, 'just-listed', 'marketing_flag');
        }
    }

    wp_reset_postdata();
}
add_action('init', 'remove_just_listed_flag');