Android installation age Is there a way to discover when my Android OS was installed? In other word: what is the age of the SO running in my phone (since the last FW upgrade)?

I have root access and I prefer not installing any extra apps to this task (altough, if it is the only way, I may install one). I already have a Terminal Emulator App.

I looked into "Settings -> About phone" and there is a counter since the last reboot, which is not what I want.

I am running Android 4.0.4 on a Sony Xperia P.
I have no idea how to know the last Android OS installation date. But if you logged in to your Google account at that day, you can search the log in date. Browse there, verify your phone model and check authorization date. Hope it works!