Windows 8 / Server 2008 set auto time sync to external NTP

Besides using GUI to setup Windows NTP sync source (in fact, in domain controller or some PC under domain, the NTP setup GUI is hidden), you may setup NTP time source via PowerShell (command prompt)

PowerShell Version:

w32tm /config /manualpeerlist:stdtime.gov.hk /syncfromflags:MANUAL
Stop-Service w32time
Start-Service w32time

Command Prompt version (if you don't have Powershell yet):

w32tm /config /manualpeerlist:stdtime.gov.hk /syncfromflags:MANUAL
net stop w32time
net start w32time

(Source)