WooCommerce Simple Storewide Sale is a plugin and excellent marketing tool which allows you to have sitewide sales like for Black Friday, Christmas, clerance, store anniversary or some other special day. You can define discount in precentage or fixed value, sale start and end date, you can exclude some products, product categories, product types, tags, add sitewide notification about sale or have notification before sales start.

Demo: https://codecanyon.net/item/woocommerce-simple-storewide-sale/14867971