17 years for each brood to emerge, but they can overlap areas. We are near the line (the Susquehanna river) between Brood X and brood II in Philly area. I know we had them less than 17 years ago, so assume it was 2013 when it shows those came out. So far we have none right now, but there are areas around Philly getting them now. All a matter of where they laid eggs last round.
