  We propose a general expression for the probability distribution of
real-valued tunneling times of a localized particle, as measured by the
Salecker-Wigner-Peres quantum clock. This general expression is used to obtain
the distribution of times for the scattering of a particle through a static
rectangular barrier and for the tunneling decay of an initially bound state
after the sudden deformation of the potential, the latter case being relevant
to understand tunneling times in recent attosecond experiments involving strong
field ionization.
