When to Set Time Zone

[ProgrammerBruce]

As retrieved by TZUTIL /g, it appears that the Windows install sequence does not set the time zone to the value specified in the (not)unattend.xml until the first user login session, and that before this login session begins, the time zone "Pacific Standard Time" is used.

Is there a known issue with adding a call to set the time zone earlier on, e.g., via PowerShell Set-TimeZone at the beginning of the "System scripts" sequence?

[cschneegans]

I can confirm your observation, using an autounattend.xml file with TimeZoneMode=Explicit&TimeZone=W.%20Europe%20Standard%20Time, a custom .ps1 system script with the content

[System.DateTimeOffset]::Now.ToString('o');
[System.DateTimeOffset]::UtcNow.ToString('o');
Get-TimeZone;

and the latest Win11_25H2_English_x64_v2.iso image.

When the system script executes, it returns Pacific Standard Time. This is probably because Redmond is located in that time zone and all Windows images are built there. The local time returned by [System.DateTimeOffset]::Now also uses that time zone and corresponds with the UTC time returned by [System.DateTimeOffset]::UtcNow, so there is nothing strictly wrong here.

I would assume that by running Set-TimeZone in a system script you could indeed set the desired time zone earlier than Windows Setup would otherwise do, but I have not tested this.

It might also be possible to set the time zone by changing the registry values in HKLM\mount\ControlSet001\Control\TimeZoneInformation during the PE stage by using a custom .cmd script. This would set the desired time zone before Windows even boots for the very first time, and would avoid changing its time zone while running.

[cschneegans]

It might also be possible to set the time zone by changing the registry values in HKLM\mount\ControlSet001\Control\TimeZoneInformation during the PE stage by using a custom .cmd script. This would set the desired time zone before Windows even boots for the very first time, and would avoid changing its time zone while running.

Now implemented via b421f10. Fortunately, dism.exe /Image:… /Set-TimeZone:"…" makes this both easy and reliable, without manually setting registry values.

Both conditions must be true:

• The Generate a .cmd script using the form's other settings and also these options must be selected.
• The Set your time zone explicitly must be selected. I make no attempt to derive the time zone from region settings.

When I check the events in the System log later, they indeed all use the same time zone, without the gap that would otherwise occur.