  Quantum reference frames have attracted renewed interest recently, as their
exploration is relevant and instructive in many areas of quantum theory. Among
the different types, position and time reference frames have captivated special
attention. Here, we introduce and analyze a nonrelativistic framework in which
each system contains an internal clock, in addition to its external (spatial)
degree of freedom and, hence, can be used as a spatiotemporal quantum reference
frame. We present expressions for expectation values and variances of relevant
observables in different perspectives, as well as relations between these
quantities in different perspectives in scenarios with no interactions. In
particular, we show that even in these simple scenarios, the relative
uncertainty between clocks affects the relative spatial spread of the systems.
