  Starting from an associated reparametrization-invariant action, the
generalization of the BRST-BFV method for the case of nonstationary systems is
constructed. The extension of the Batalin-Tyutin conversional approach is also
considered in the nonstationary case. In order to illustrate these ideas, the
propagator for the time-dependent two-dimensional rotor is calculated by
reformulating the problem as a system with only first class constraints and
subsequently using the BRST-BFV prescription previously obtained.
