Time is not an illusion, but driven by energy turnover
I defined energy with a tendency to decrease its presence per state. Time then would be the trace of changes which energy carves into the environment and into our selves on its irreversible way from non-equilibrium to equilibrium. Since energy and time are linked they can only be transformed together to a frame with different velocity in form of action, energy times time. Action however remains the same when transformed between references with different velocities. Time travel is consequently impossible. Time alone, without action should not exist in nature or in our brain. To get the time flowing, action has to occur and if our brain needs to monitor time, it has to divide this action by the energy turned over.
Fig.: Time is not an illusion. Compare my picture with that one on the startpage.