  It is well known that unitary symmetries can be `gauged', i.e. defined to act
in a local way, which leads to a corresponding gauge field. Gauging, for
example, the charge conservation symmetry leads to electromagnetic gauge
fields. It is an open question whether an analogous process is possible for
time reversal which is an anti-unitary symmetry. Here we discuss a route to
gauging time reversal symmetry which applies to gapped quantum ground states
that admit a tensor network representation. The tensor network representation
of quantum states provides a notion of locality for the wave function
coefficient and hence a notion of locality for the action of complex
conjugation in anti-unitary symmetries. Based on that, we show how time
reversal can be applied locally and also describe time reversal symmetry twists
which act as gauge fluxes through nontrivial loops in the system. As with
unitary symmetries, gauging time reversal provides useful access to the
physical properties of the system. We show how topological invariants of
certain time reversal symmetric topological phases in $D=1,2$ are readily
extracted using these ideas.
