You want to know the uptime for devices like Management Center/SSLV Appliance/Content Analysis/Reporter/Edge SWG:
To check the uptime using CLI use the following command for devices like Management Center/Content Analysis/SSP/Reporter/SSLV Appliance:
Device> enable
Password:
Device# diagnostics heartbeat view
} ],
"uptime" : "4 days 20 hours 49 minutes"
},
The output of the above commands contains a JSON object uptime with the uptime value.
To check the uptime for Proxy device use the article : https://knowledge.broadcom.com/external/article/166312/how-to-check-the-system-uptime-in-the-pr.html