Sort Events Category by Publish Date (Oldest First)

function sort_posts_by_category($query) {

    if ($query->is_main_query() && !is_admin()) {

        $oldest_first_categories = array(1483,1486,1485,1484,1482,1391); // Replace with the IDs of the categories where you want to display oldest posts first

        if (is_category($oldest_first_categories)) {

         //   $query->set('order', 'ASC');

        //    $query->set('orderby', 'date');

			$query->set( 'meta_key', 'start-date' );

            $query->set( 'orderby', 'meta_value' );

            $query->set( 'order', 'ASC' );

        } else {

            $query->set('order', 'DESC');

            $query->set('orderby', 'date');

        }

    }

    return $query;

}

add_filter('pre_get_posts', 'sort_posts_by_category');