  Disorder is an unavoidable ingredient of real systems. Spatial disorder
generates Griffiths phases (GPs) which, in analogy to critical points, are
characterized by a slow relaxation of the order parameter and divergences of
quantities such as the susceptibility. However, these singularities appear in
an extended region of the parameter space and not just at a (critical) point,
i.e. there is generic scale invariance. Here, we study the effects of temporal
disorder, focusing on systems with absorbing states. We show that for
dimensions $d \geq 2$ there are Temporal Griffiths phases (TGPs) characterized
by generic power-law spatial scaling and generic divergences of the
susceptibility. TGPs turn out to be a counterpart of GPs, but with space and
time playing reversed roles. TGPs constitute a unifying concept, shedding light
on the non-trivial effects of temporal disorder.
