  The Two-State-Vector formalism and the Entangled Histories formalism are
attempts to better understand quantum correlations in time. The main objective
of this paper is to show that, with appropriately defined scalar products, both
formalisms can be made isomorphic. We show that they treat operators and states
on equal footing leading to the same statistics for all measurements. In
particular, we discuss the topic of quantum correlations in time and show how
they can be generated and analyzed in a consistent way in these formalisms.
Furthermore, we elaborate on a novel behavior of quantum histories of evolving
multipartite systems which do not exhibit global non-local correlations in time
but nevertheless can lead to entangled reduced histories characterizing
evolution of an arbitrarily chosen sub-system.
