How to configure time service in Windows Servers

Change the Windows Time service configuration on the previous PDC emulator

Open a command prompt and type the following commands:
w32tm /config /syncfromflags:domhier /reliable:no /update
W32tm /config /update
W32tm /resync

On a Windows Server 2008 R2 enter these commands:
net stop w32time
w32tm /register
net start w32time

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Configure the PDC emulator to synchronize from its internal hardware clock

Open a command prompt and type the following commands:
w32tm /config /syncfromflags:domhier /reliable:yes /update
W32tm /config /update
W32tm /resync

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Configuring the forest root domain PDC FSMO to use an another time source

Open a command prompt and type the following commands:
W32tm /config /manualpeerlist:"212.251.14.84 192.108.114.23 193.93.167.241" /syncfromflags:manual
W32tm /config /update
W32tm /resync

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Query sntp servers

Open a command prompt and type the following command:
net time /querysntp

Also take a look at these articles:
http://theessentialexchange.com/blogs/michael/archive/2010/01/29/a-brief-history-of-time-ok-ok-let-s-go-with-quot-an-introduction-to-the-windows-time-service-quot.aspx
http://technet.microsoft.com/en-us/library/cc773061%28WS.10%29.aspx