Windows Time Service
Configuring the time service on the PDC Emulator FSMO role holder
Change the Windows Time service configuration on the previous PDC emulator
http://technet.microsoft.com/en-us/library/cc738042(v=ws.10).aspx
Windows Time Service Tools and Settings
http://technet.microsoft.com/en-us/library/b43a025f-cce2-4c82-b3ea-3b95d482db3a
Configuring And Managing The Windows Time Service
Demystifying Group Policy Settings
http://blogs.msdn.com/b/w32time/archive/2009/02/02/group-policy-settings-explained.aspx
Configuring an Authoritative Time Server with Group Policy Using WMI Filtering
High Accuracy W32time Requirements
http://blogs.technet.com/b/askds/archive/2007/10/23/high-accuracy-w32time-requirements.aspx
How the Windows Time service works on an RODC
http://technet.microsoft.com/en-us/library/cc754218(WS.10).aspx#BKMK_Time
For virtual DCs; dont sync the time with the host machine. For Hyper-V you need to disable the Hyper-V time service. You need to disable the below service for DCs.
Keeping the Domain On Time-Time Source Selection
<>A machine can only look for a time source in its own domain or the parent domain. A machine will never go to a domain on a parallel level, or a "skip-level" parent domain.
<>Within a domain, a machine cannot sync with its own kind. A DC cannot sync with another DC. A client cannot sync with another client.
http://blogs.msdn.com/b/w32time/archive/2007/09/04/keeping-the-domain-on-time.aspx
MSDN
Windows Time Service