No date code on any of the Nokian tires that I have here. Most of bicycle tires don't last very long anyway, and they are thin enough to show obvious signs of aging on shelves.
Nevertheless, I ride one "new old stock" 10yr old 3.0 Gazzaloddi on the front right now and it is still a very good tire. Rubber ages fine on the shelves if it is not exposed to sun light.