I have not played with FMC reporting that level.
But we do have Monitoring system outside FMC - NMS can do that work for you, if you using SNMP also on FTD you can use uptime command or show version command show you how long the uptime of the device.
if they are high availability in pair then you see different results in GUI.
On the GUI of FMC - FMC reports Up Time. It's listed under System ---> Monitoring ----> Statistics