A rotating frame is defined in reference to an inertial frame of reference. Consider a beach ball spinning in my hand. which way is it spinning? If we judge it by comparison to me, it might be spinning, say, clockwise around the axis perpendicular to my hand. I'd we judge it in comparison to the sun, that answer changes.
I still think I'm right here, but welcome attempts to fix my faded memories of physics.
The direction of rotation is relative, but the fact that it is rotating is not. That is, an observer in the Sun's reference frame can, indeed, determine that the Sun is rotating. (The Coriolis effect is one example.)
I still think I'm right here, but welcome attempts to fix my faded memories of physics.