Configuring Windows 7 support for UTC BIOS time

Windows 7 does not natively support UTC time. Which makes it a problem if you’re also running either Linux or OSX on the same machine. Either way having your BIOS keep time using UTC is the proper way.

  • Universal Time can be unambiguously converted into a local time. The opposite is not true, that is a local time cannot reliably be converted back into Universal time. This is due to the Summer Time or Daylight Savings Time offset periods implemented in many countries. At the end of that offset period, local-time clocks have to be turned back by usually one hour, therefore a 60 minute period on the local-time scale is repeated.
  • Daylight Savings Time makes it necessary to readjust the RTC twice per year. However, there exists currently no convention to label in the CMOS RAM, whether that adjustment has already been performed or not. As a result, the operating systems can get confused and will apply the correction multiple times. One possible fix is to record somewhere on the hard disk, whether the DST change has already been performed this year or not. However this fails for users who have a requirement to run several operating system versions in different hard disk partitions on the same computer, where the same RTC is shared by several operating systems that can be booted alternatively but do not have access to each others configuration files. A similar problem occurs when the operating system is booted from some exchangeable storage medium or a PC-in-PC emulator is used.

To enable UTC support please do the following.

Copy the following into a text document using notepad and save it as utc.reg

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TimeZoneInformation] ‚ÄúRealTimeIsUniversal‚ÄĚ=dword:00000001

Run it, reboot and you’re done.

Or do the following

  • Start the Registry Editor (regedit)
  • Traverse the following path, HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TimeZoneInformation
  • Create a dword named RealTimeIsUniversal and set the value to 1
  • Restart your computer

// CrashMAG

3 thoughts on “Configuring Windows 7 support for UTC BIOS time”

  1. Hello.
    It worked perfectly.
    I have done what you explain here, it is, saving these commands on a notepad document and changed its extension to “.reg”, combined later in the registry and restarted. The time is what have to be, and rebooted once again in my GNU/Linux too… and the time keep being what it have to be.
    Thanks you so much, big hug for you from Uruguay.

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