All at the same time ? Looks like a expired certificate for boot image signing. 1) Connect them to a network with fake NTP servers serving the time from last week. -or- 2) Open them up, remove whatever battery is on the main board for 15 sec, the start them without a network connection.
1) Great suggestions!
2) Anyone else getting tired of all of our toys' continued functionality being at the mercy of some corporation. Seems like they make them, sell them and forget them and do it all over again with the next model.
"More software projects have gone awry for lack of calendar time than for all other causes combined." -- Fred Brooks, Jr., _The Mythical Man Month_