New badge

function king_new_badge_shop_page() {

   global $product;
   $new_counter = 30;
   $product_created = strtotime( $product->get_date_created() );

   if ( ( time() - ( 60 * 60 * 24 * $new_counter ) ) < $product_created ) {
        return '<span class="newbadge onsale">_YOUR_CUSTOM_BADGE_TEXT</span>';
   }
   else{
        return;
   }
}

add_action( 'woocommerce_sale_flash', 'king_new_badge_shop_page', 3 );