In
time standards,
dynamical time is the time-like argument of a dynamical theory; and a
dynamical time scale in this sense is the realization of a time-like argument based on a dynamical theory: that is, the time and time scale are defined implicitly, inferred from the observed position of an astronomical object via a theory of its motion. A first application of this concept of dynamical time was the definition of the
ephemeris time scale (ET).