  Weak measurements offer new insights into the behavior of quantum systems.
Combined with post-selection, quantum mechanics predicts a range of new
experimentally testable phenomena. In this paper I consider weak measurements
performed on time-dependent pre- and post-selected ensembles, with emphasis on
the decay of excited states. The results show that the standard exponential
decay law is a limiting case of a more general law that depends on both the
time of post-selection and the choice of final state. The generalized law is
illustrated for two interesting choices of post-selection.
