What about rotation, though? E.g. if you fix a coordinate system on Earth, then it rotates through the entire universe on a daily basis.

We might want to use something like the International Celestial Reference Frame (ICRF), which is designed to avoid rotation with respect to certain distant extragalactic objects.

You'd also need to take the expansion of the universe into account. You'd really need to start using comoving coordinates (https://en.wikipedia.org/wiki/Comoving_and_proper_distances)

It could make sense to sell spacetime worldtubes instead.

> geological time scale

Things appear to move slowly when viewed from the origin of the coordinate system, but unless you take steps to avoid it, like using comoving coordinates, then at great distances the motion of any given parcel would be enormous relative to local matter, easily exceeding the speed of light.