Is there a way to pull up information regarding when a network device reboots or cuts power?

I am currently testing switches(Cisco & HP). However, power turns off from time to time at these locations. I've been attempting to see if maybe there was a log command that allowed a user to look at when the network switch power cycled/rebooted. The closest command that I have been able to find is "uptime". But this only shows the uptime from the last boot instance.