  A four dimensional treatment of nonrelativistic space-time gives a natural
frame to deal with objective time derivatives. In this framework some well
known objective time derivatives of continuum mechanics appear as
Lie-derivatives. Their coordinatized forms depends on the tensorial properties
of the relevant physical quantities. We calculate the particular forms of
objective time derivatives for scalars, vectors, covectors and different second
order tensors from the point of view of a rotating observer. The relation of
substantial, material and objective time derivatives is treated.
