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Since I live in Germany, my timezone is GMT+1 (or GMT+2 in the summertime period). Previous Windows versions were not able to have the hardware clock set to UTC, and the Windows time to the local time. That was / is a big mess, since almoust every other OS is using UTC preferedly.

Is this fixed in Windows 7 and is it now possible to use UTC in the BIOS and local time in Windows?

Mika Fischer
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mru
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3 Answers3

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Have a look at this page:

Save the following lines as utc.reg, and then run it to import this registry tweak. It allows you to set the hardware clock in your PC’s BIOS to UTC time. This is handy for boot dual-booting Mac, or Linux, when those operating systems are set to read the BIOS clock as UTC time, instead of Windows’ preferred Local Time (e.g., PST, PDT, MST, MDT, CST, CDT, EST, EDT, or the standard “GMT-” and “GMT+”)

Here is the code to save as utc.reg:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TimeZoneInformation]
"RealTimeIsUniversal"=dword:00000001

The equivalent answer can also be found here.

Jacob Peddicord
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subanki
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    Make sure you read the notes at http://www.cl.cam.ac.uk/~mgk25/mswish/ut-rtc.html - the RealTime option still has several glitches. – u1686_grawity Sep 07 '10 at 20:27
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    Ok, i knew this registry hack from former Windows versions and i thought in 2010 perhaps they've got managed to get such easy things as UTC support officially working. Unfortunately it doesn't seem so. – mru Sep 19 '10 at 15:26
  • Does this work with Windows 8? – pratnala Oct 28 '12 at 12:05
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    @PratyushNalam Yes, it works with Windows 8. I just set it up. – Michael Hampton Nov 29 '12 at 17:46
  • Reading the link posted in another comment, I'm greatly encouraged by more recent updates at the link added since this answer was written reporting on patches issued by MS for this registry key. That they are issuing patches indicates the key **is** supported and that you _should_ now expect it to work just fine. – Joel Coehoorn Jul 06 '15 at 05:09
  • I tried exactly this way, but my system says that it can only merge a **binary** registry file and refuses to do this with the plain text `utc.reg`. Anyway, I've changed this setting directly through regedit. (I haven't yet tested whether it works, because I assume I need to reboot to see the effect, so I went to reboot the system to see the effect, but have just booted the other GNU/Linux system and not Windows yes.) Thanks a lot to everyone involved for discovering and posting this hint; I hope it works. – imz -- Ivan Zakharyaschev Sep 07 '15 at 23:57
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    This can be applied in single line `reg add "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TimeZoneInformation" /f /v RealTimeIsUniversal /t REG_DWORD /d 1` – user2209299 Apr 09 '17 at 11:34
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Windows 7 support for UTC time in the RTC is at this time incomplete (July 2013), and not recommended by sysadmins who have tried to make use of it.

The site recommended by grawity above includes a useful summary of the state of this problem.

Currently, if you enable "RealTimeIsUniversal", occasionally the system time gets reset to a wrong time (UTC minus local offset). This causes the DHCP client to fail to refresh the dhcp lease and the system becomes disconnected until you manually refresh the lease, or restart the DHCP client.

Finding a workaround for this particular bug may be an acceptable tradeoff, but there might be other subtle bugs that come and go as Windows gets updated, due to the fact that the "RealTimeIsUniversal=1" configuration is not regression tested at Microsoft presently.

drok
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I want to add this link http://www.nathanhunstad.com/blog/2012/01/windows-7-utc-time-issue/ in which explains that sometimes Windows doesn't update the BIOS clock, but does make the UTC->Local time conversion.

The key is to make the change in the BIOS manually and Windows won't change it. It also speaks that Internet Time won't work correctly.

Hope it's interesting for you and find it usefull!

txomon
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    Please post all relevant information from links into your answer, this will help avoid link rot – 50-3 Sep 12 '13 at 01:26
  • What did I miss? – txomon Sep 12 '13 at 08:45
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    you have linked an article (I think I can't open the link) I was just saying that this link is unlikely to exist forever if there was any extract from the article you could use to further explain your answer please include it in your answer – 50-3 Sep 12 '13 at 21:10
  • Well, this is meant to be an addition to the official and selected answer. I already wrote the important parts of it. (in which explains...) – txomon Sep 13 '13 at 08:16