Koji je danas datum? means “What’s today’s date?”
You look at your calendar and see that today you were going to buy Japanese ornamental fish, and in Jena of all places: koi and Jena give you koji je. These fish eat nothing but dates and pineapple – date and pineapple (Ananas in German) give you danas. And on each packet is the date you bought them.
Danas for “today” gets its own video later on – here you pick it up along the way.