Microsoft® Windows® and Zulu Time.

Although many would agree that computer's hardware clock should run in Coordinated Universal Time (UTC), Microsoft took a different approach and force everyone to set the hardware clock (RTC or BIOS CMOS time) to the local time that causes a number of problems. In my opinion, here is the best article summarizing all those problems. To use hardware clock running in UTC with Windows® NT or better, add to the registry

\HKLM\SYSTEM\CurrentControlSet\Control\TimeZoneInformation

DWORD key "RealTimeIsUniversal=1" (it is undocumented and does not exist by default).

Reboot your PC, enter BIOS Setup and set the time according to Greenwich. On next reboot Windows® will set the system time according to the time zone you use and UTC obtained from RTC.

Known issues

• Windows® does not honour this undocumented registry key while waking up from standby or hibernate mode. As a result the system time of woken up Windows® will be few hours off. Despite it looks like should be called the same procedure to get system time from CMOS on waking up from deep sleep or on cold boot, it’s not the case. Only Microsoft can solve this problem. There is no known hacks or system patches so far. As a workaround you may disable standby and hibernate modes. Go to "Control Panel" > "Power Option", this will open "Power Options Properties" dialog. Check every tab in this dialog as everywhere there is a possibility to leave standby or hibernate mode enabled.
• If you do not use time synchronizing software like "Windows Time", there is yet another surprise from Microsoft called "Time Daemon". You can read more detailed about it in article KB232488. Briefly, this Daemon (latest MSDN documentation refers to the Daemon as a system’s internal adjustment mechanism) periodicaly checks system time and hardware time. If the two times are more than one minute apart, Windows changes the time and date to match the RTC. Obviously, the Daemon does not check the undocumented key in registry. Thereby the system time jumps from local to UTC in an hour. A workaround for this problem provided below.

tymesync.exe

Why I think that a system time jump is a Bad Thing^TM is a way beyond this discussion. What is essential, your Windows® computer without time synchronizing service may experience the jumps of the system clock, and Microsoft guarantees these time jumps will not be less than one minute. That was a good reason to write a small utility tymesync.exe that does nothing but disable the Daemon. It supports the command line options for quiet execution. You can schedule this utility to run on system start by adding it to the registry

\HKLM\Software\Microsoft\Windows\CurrentVersion\Run

	timesync.exe with no options will display dialog as shown on the screenshot. If any valid option specified on command line, it will do the job without the dialog.
	Options are:
	timesync.exe -d - disable Time Daemon;
	timesync.exe -e - enable Time Daemon.

Known issues

• If you turn on the computer and do not log in in an hour, the Daemon will have a chance to "adjust" the system time;
• If you have some quite restricted user’s account and that user logs in first after shutdown or reboot, the timesync.exe will not have enough privileges to disable the Daemon.

Both these issues could be easily resolved by installing the utility as a system service. Grep internet for srvany.exe and instsrv.exe, more specifically the Windows NT/2000 Resource Kit provides these utilities.

And finally, don’t forget to grep your QNX start up scripts in order to remove -l ("el") option from the rtc command, assuming you use dual boot system.

©2004-2009, Eduard Kromskoy