So it doesn't matter if I set "Set time automatically" to off or go to internet time and disable the synchronizing with the server (and I turned off adjusting for dst too), windows still changes my time to my current timezone after a restart or a few hours.

I checked the "Windows Time" service also and it's disabled. This not only happens in a single PC, all my machines have this problem. Am I doing something wrong here?

I have no additional clocks or weird stuff like that. Just a plain installation will work as described. I also can't just "choose the right timezone". That's not a solution, cause it's the minutes I want to change.

Any ideas why Windows keeps synchronizing my time when it shouldn't?

If these PCs are part members of a Active Directory domain, then this is the default behavior.

The Kerberos system that is used as part of the authentication of domain accounts uses a strict "time out" system in order to prevent a "replay" attack. The idea is that the time stamps on each request/response must be within an acceptable windows of tolerance (5 minutes by default). So, to keep Kerberos working, all domain members sync their clocks with the domain controller by default.

https://technet.microsoft.com/en-us/library/cc779260%28v=ws.10%29.aspx?f=255&MSPPError=-2147217396

So, that means if you are somehow able to alter the time on your PC by more than 5 minutes, you won't be able to be authenticated on that PC via Active Directory.

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\DateTime\Servers

As a last resort, delete the servers in the registry.