IMHO, You are over-thinking/complicating this.

When I was working at Nvidia, I worked on a multi-boot OS image that
had every current flavor of Windows/Linux that the GPUs needed to be
tested on behind GRUB (the old GRUB, where you could tell it which OS
to boot to without running shell scripts).  We "fixed" this same
problem by telling Windows to expect UTC BIOS clock and not to do
network time syncs (yes this works even with Windows 10, if you get
the QWORD/DWORD sizes right).  Clock drift in Windows is negligible
even after a few days, but you can either suspend or reboot triggering
a new read from HwRTC to clear that up.

There is a lot of information on how to set the Windows registry on
the interwebs, and Win8+ has a UTC option on the time control panel
now.  One of the trickiest issues we ran into is some Linux flavors
using an offset from the hardware clock rather than reading and
writing to the clock directly - you need to understand how all of the
time daemons do their thing on your chosen OSes.


> Date: Sat, 10 Mar 2018 14:07:22 -0500
> From:
> To: "" <>
> Subject: [coreboot] Can coreboot automatically detects Windows/Linux
>         and provide local/UTC time accordingly?
> Message-ID:
> <>
> Content-Type: text/plain; charset="utf-8"
> I use both Windows and Linux, try different versions and distributions, and 
> often do clean install of these systems. An problem I faced is the default 
> install of Windows takes the time provided by the board as local time, while 
> Linux takes it as UTC time. After every installation, the first thing I have 
> to do is to configure it.
> So instead of configure it at the system level, can this be done at the 
> coreboot/seabios level? Can coreboot or seabios automatically detect the 
> system it is running? Can it automatically provides local time if it detected 
> Windows, while provides utc time when it detected Linux?

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