On each cruise, there are three rotations. The rotations vary by ship and itinerary.
On our Alaskan cruise last year, the rotations were based on the pattern 1223123.
So for the three restaurants (T=Triton's, A=Animator's Palate, P=Parrot Cay), the three possible rotations were TAAPTAP, APPTAPT, and PTTAPTA.
You can call
DCL and ask them what the rotations for your cruise are. They can also tell you which nights are special events like Formal Night and Taste of Alaska. You can ask for a specific rotation, but it is not guaranteed (though if you are traveling Concierge, you are likely to get your requested rotation).
Note: It's may be way too soon to get this information for your cruise that is more than a year away. I called to ask about dining rotations for our cruise this December and was told they don't have the rotations finalized yet.