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I ran w32tm /stripchart /computer:time.windows.com just for fun and found out that my clock is 1.3 seconds behind this timeserver. Not that I think Microsoft is wrong, but I tried it with various other timeservers in my city just to eliminate potential network delays. Same result.

The obvious way to fix this would be to force a resync, so I ran w32tm /resync, but the time difference persisted.

When I executed w32tm /query /status to find out what was causing this problem, I was shocked to find out that the default time-data source for my computer was Local CMOS Clock and has apparently never been synced to anything!

I thought I had figured out what was going on and quickly added a few timeservers to my peers using the following command: w32tm /config /manualpeerlist:ntp1.scc.kit.edu /syncfromflags:manual /reliable:yes /update.

But even after another resync, the time difference stayed at 1.3 seconds? What is going wrong?

Grunzwanzling
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2 Answers2

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Turns out w32time simply sucks. Microsoft admitted that

w32time cannot reliably maintain sync time to the range of 1 to 2 seconds.

Great software guys...

I installed a different implementation of the NTP protocol from Meinberg, a company that actually knows what it is doing: NTP Download

And boom: My time difference instantly fell to only a few ms.

23:43:23, d:+00.0135611s o:+00.6267124s
23:43:25, d:+00.0169653s o:+00.6379619s 
23:43:28, d:+00.0145823s o:+00.0086838s  <-- Exact moment the new NTP implementation was installed.
23:43:30, d:+00.0157926s o:-00.0037974s
Grunzwanzling
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    The Windows Time Service prior to Windows 10 and Windows Server 2016 was designed to meet specific requirements, which it did. It wasn't designed to be a highly accurate time service, which it isn't. There's nothing wrong with Microsoft. - https://support.microsoft.com/en-us/help/939322/support-boundary-to-configure-the-windows-time-service-for-high-accura – joeqwerty Feb 28 '18 at 22:56
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    @joeqwerty I am running Windows 10. Is there a better solution for me to use directly provided by Microsoft? – Grunzwanzling Feb 28 '18 at 23:03
  • The article lays out what needs to be done to meet your time accuracy requirements. – joeqwerty Feb 28 '18 at 23:06
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https://github.com/MicrosoftDocs/windowsserverdocs/issues/2065#issuecomment-544785547

That is what you need to do to have precise time in w32tm.

So, you need HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Parameters\NtpServer time.google.com,0x5 time.cloudflare.com,0x1 at least 2 more (in your country and in your local IX or University) https://gist.github.com/mutin-sa/eea1c396b1e610a2da1e5550d94b0453

Now do this from all tabs https://docs.microsoft.com/en-us/windows-server/networking/windows-time-service/configuring-systems-for-high-accuracy?tabs=MaxPollInterval#registry-settings

Валерий Заподовников
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