  One manifestation of quantum resonances is a large sojourn time, or
autocorrelation, for states which are initially localized. We elaborate on
Lavine's time-energy uncertainty principle and give an estimate on the sojourn
time. For the case of perturbed embedded eigenstates the bound is explicit and
involves Fermi's Golden Rule. It is valid for a very general class of systems.
We illustrate the theory by applications to resonances for time dependent
systems including the AC Stark effect as well as multistate systems.
