You can see the event log with
This assumes you have enabled logging:
logging buffered 32768 informational
Note that if someone unplugs the device, it's not going to log that event.
show logging displays the event log. For some events, you can (and may need to) explicitly configure logging.
Additionally, you can log to an external (syslog) server which can store more entries than the limited internal log and doesn't lose its entries on power loss.