You can use it anytime, but only in the Main Dining Rooms, along with the adult exclusive restaurants (Palo/Palo Steakhouse and Remy/Enchante). So if you're in the MDR for lunch (or Enchante for lunch on the Triton (Wish) Class ships, or Palo/Palo Steakhouse/Remy for brunch), and you want to finish a bottle of wine you opened the night before at dinner or order a new bottle off of your package, you can do that.