This may sound contradictory, but I believe that time is simotanious.
The past, present and future exist at once. Spirits see this and are apart of the flow of the river, where we can only percieve moments. We see time as a snapshot of the When we are now, nothing else. The dead and the spirits see it as the When they choose to interact with.
So, when you call to a spirit in Theory you could be speaking to them the moment after they died, or a thousand years down the line. Quite interesting no?