He mentally calculated in his mind. The journey from Castle Black to Winterfell on foot would take a little longer than a moon. After calling the knights of the Vale, it would take at least a fortnight for all of them to arrive, and the journey from the Eyrie to Moat Cailin would have them pass through the Riverlands, a disputed territory. It would take at least a moon's turn to reach Moat Cailin by horse after the forces finished mustering, and that is if they met absolutely no problems on the way.