This morining I decide to upgrade my workstation to Windows 11. Let me remind you that Windows 11 got some system requirments and one of the most important is "TPM 2.0". After upgrade completed, my Windows 11 shows up as below: A little more Mac-like look system tray I think.
Let's take a look at my workstation, what's the InstallDate as below? Use any Epoch & Unix timestamp conversion tools to convert the unix numeric timestamp and you could find the answer is 2121/10/10. That's exactly the day I upgrade my PC to Winodws 11.
It goes without saying that major Windows Update could change the timestamp of "InstallDate". That means "InstallDate" is not the day OS being installed in the first place. You could take a look at event logs and observe the MACE timestamp of files and you won't be fooled by the "InstallDate" any more.