[ntp:questions] questions] Automatic time synchronization of local hw clock.

Martin Burnicki martin.burnicki at meinberg.de
Tue Apr 22 09:34:01 UTC 2014

Brian Inglis wrote:
> On 2014-04-19 16:16, Casper H.S. Dik wrote:
>> Jos van de Ven <antispam at vdven.org> writes:
>>> The registry key is:
>>> HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TimeZoneInformation
>>> And then add a DWORD (32bit) value and name it RealTimeIsUniversal
>>> with a
>>> value of 1
>>> It should be working with windows 8 also, but I don't use that.
>> I tried it under Windows XP and there it didn't work (it worked until
>> you suspended the system; then the time got very confused)
> You have to set the BIOS time to UTC ASAP.
> Try this:
> Copy the following lines to a DOS <cr-lf> line ending text file e.g.
> WindowsUTC.reg:
> Windows Registry Editor Version 5.00
> [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TimeZoneInformation]
>       "RealTimeIsUniversal"=dword:00000001
> Import to registry immediately before rebooting.
> During reboot go into BIOS setup time settings and set the RTC to UTC time
> (and zone or no DST) by subtracting your UTC offset or using a UTC
> reference.
> Save and Exit BIOS setup and continue rebooting.
> Windows will come up using the RTC time directly to set the system to UTC
> but your logon time zone settings will be used normally for display.

See this page:

Markus Kuhn: IBM PC Real Time Clock should run in UT

for a summary of potential problems using this registry key, especially 
the section "Current support status in Windows".

Martin Burnicki

Meinberg Funkuhren
Bad Pyrmont

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