.This is an extended discussion of the introduction and role played by the so-called co-rotational derivative (also called the Jaumann derivative in Germany and, rightfully, the Zaremba derivative in Poland) and other "objective'' time derivatives of geometrical objects as they appear in continuum physics. This is achieved in a somewhat abstract formalism starting with clearly defined "spatial" and "material" notions, the differentiable-manifold definition of deformation tensors, and the notions of parallel transport and Lie derivative. The notion of "objectivity'' (as common in continuum mechanics since the pioneering work of W. Noll) and Piola transformations follow next. The paper ends with a reminder on local balance equations and objec...