  Existing tensor network models of holography are limited to representing the
geometry of constant time slices of static spacetimes. We study the possibility
of describing the geometry of a dynamic spacetime using tensor networks. We
find it is necessary to give a new definition of length in the network and
propose a definition based on the mutual information. We show that by
associating a set of networks with a single quantum state and making use of the
mutual information based definition of length, a network analogue of the
maximin formula can be used to calculate the entropy of boundary regions.
