I have a custom field called "value_date" where add a date 
e.g yyyy/mm/dd

The idea is sort the upcoming dates first in the loop, is possible?

I used a template for custom post taxonomy-event-date.php and this is code in the function, It doesn't work.

**Functions.php**

    add_action('pre_get_posts','search_filter');
    function search_filter($query){
        if ( !is_admin() && $query->
    is_tax( 'event', 'date' ) ) {
            $today = date( 'Y-m-d' );
            $query->set('post_status', 'publish');
            $query->set('meta_value', $today);
            $query->set('meta_key', 'value_date');
            $query->set('orderby', 'meta_value_num');
            $query->set('order', 'ASC');
        }
    }