  We present an implementation of a recently proposed procedure for defining
time, based on the description of the evolving system and its clock as
non-interacting, entangled systems, according to the Page and Wootters
approach. We study how the quantum dynamics transforms into a classical-like
behaviour when conditions related with macroscopicity are met by the clock
alone, or by both the clock and the evolving system. In the description of this
emerging behaviour finds its place the classical notion of time, as well as
that of phase-space and trajectories on it. This allows us to analyze and
discuss the relations that must hold between quantities that characterize
system and clock separately, in order for the resulting overall picture be that
of a physical dynamics as we mean it.
