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I'm looking for information on how the Windows TIme Service over a domain affects the hardware clock. The machines are clients on a Windows AD domain with the basic time services. It's not our network so I don't have a lot of detail.

1) We are doing some transaction based processing with a remote host. We normally see the a difference of about 250 ms between OS clocks included network delays. This is fine.

2) If the computer is rebooted the difference is about 10 seconds. It takes about 30 minutes to get back down to the 250 ms again. I believe this is called convergence.

I'd like some direction on where to look for information regarding:

a) Does the Windows Time service ever update the real-time hardware clock to keep it close? b) Is there a way to tell the Time service to do a faster convergence? c) I think this service is a bit different from NTP which could be configured. Right?

My searches have not addressed the RTC and ways to speed up the convergence.

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migrated from stackoverflow.com Sep 4 '10 at 18:12

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2 Answers 2

Use NET TIME /SET /Y if the clock is beyond the convergence threshold (can't remember the default value). Otherwise, the Windows Time Service can be given a "poke" using w32TM /RESYNC.

There's also some useful switches for monitoring the convergence progress: /MONITOR and /STRIPCHART.

Make sure you have >1 reliable time sources, preferably three.

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It looks like we are going to use a the NET TIME command to sync to the system clock. Specifically NET TIME /SET /Y will be run at start up. It will set the time immediatly rather than slowly converging. The time server used is reported when running that command so we can insert it into the batch file.

NET TIME \myTimeServer /SET /Y will go directly to the server speeding things up. As a fail safe we can check the return code in case the server is unvailable and run it with out the name as in the first example.

If you can't directly reach the time server, you can set it to the domain PDC clock using this command. This is probably pretty good as a second choice. NET TIME /domain:myDomain /SET /Y.

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A little update for those that find this thread. We found we were getting a drift over an eight hour period of up to almost 2 seconds between clocks. This is as outlined by Microsoft that does not guarantee anything less than 2 seconds. Running the NET TIME command as above every two hours we are able to keep the machines within 800 ms. –  user53568 Sep 22 '10 at 20:36

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