Remove tribe-bar-date z-index

add_filter('tribe-events-bar-filters', 'reduce_tribal_z_index');

function reduce_tribal_z_index(array $filters) {
    if (isset($filters['tribe-bar-date']['html']))
        $filters['tribe-bar-date']['html'] = str_replace('z-index:10000', '', $filters['tribe-bar-date']['html']);

    return $filters;
}