  We use holography in order to study the entanglement entropy for a spherical
entangling surface in a FRW background with an arbitrary time dependence of the
scale factor. The calculation is done in various dimensions, allowing for
nonzero spatial curvature. The entanglement entropy of a CFT at nonzero
temperature in this background is also considered. Our approach is based on
coordinate transformations that relate the extremization problem to the one for
a static background, with a careful determination of the UV cutoff. We
demonstrate the agreement with the expected form of the entanglement entropy
and with various known results in specific cases. In four dimensions, apart
from the cutoff-dependent terms, we compute and discuss the finite term related
to the expansion rate.
