  We investigate quantum correlations in time in different approaches. We
assume that temporal correlations should be treated in an even-handed manner
with spatial correlations. We compare the pseudo-density matrix formalism with
several other approaches: indefinite causal structures, consistent histories,
generalised quantum games, out-of-time-order correlations(OTOCs), and path
integrals. We establish close relationships among these space-time approaches
in non-relativistic quantum theory, resulting in a unified picture. With the
exception of amplitude-weighted correlations in the path integral formalism, in
a given experiment, temporal correlations in the different approaches are the
same or operationally equivalent.
