  We introduce a real time version of the functional renormalization group
which allows to study correlation effects on nonequilibrium transport through
quantum dots. Our method is equally capable to address (i) the relaxation out
of a nonequilibrium initial state into a (potentially) steady state driven by a
bias voltage and (ii) the dynamics governed by an explicitly time-dependent
Hamiltonian. All time regimes from transient to asymptotic can be tackled; the
only approximation is the consistent truncation of the flow equations at a
given order. As an application we investigate the relaxation dynamics of the
interacting resonant level model which describes a fermionic quantum dot
dominated by charge fluctuations. Moreover, we study decoherence and relaxation
phenomena within the ohmic spin-boson model by mapping the latter to the
interacting resonant level model.
