A required time calculator calculates a virtual required time period when a first movable body is assumed to travel a second route different from a first route the first movable body actually travels and arrive at a second point. The required time calculator preferentially acquires position information from a second movable body having information indicating a movement characteristic similar to information indicating the movement characteristic of the first movable body from among one or more of second movable bodies. The required time calculator calculates the virtual required time period using the acquired position information.