Hi,
I can't find a CLI command for that but you can see through SNMP the uptime of the switch when the port changed state for the last time.
The OID is .1.3.6.1.2.1.2.2.1.9 - ifLastChange:
The value of sysUpTime at the time the interface entered
its current operational state. If the current state was
entered prior to the last re-initialization of the local
network management subsystem, then this object contains a
zero value.
Hope this helps.
Best regards,
Aarón