[WildParser]

I don't really know what those people in physics do, but as a mathematician my definition of a time-crystal would be a 4-dimensional discrete structure. You have some 4-dimensional symmetries.

Just rotating in 3D is a bit boring. Interesting symmetries would be where you get the time-axis involved.

4D is most likely a bit boring - having more dimensions and more time-dimensions helps greatly to get more symmetries to work with...