This is how to configure your primary domain controller to update time from an external source.
– Login to your primary domain controller

– Open up a command prompt/powershell window with administrative privileges
 
– Execute the following command to configure the domain controller to look at an external time   source: 
 
w32tm.exe /config /manualpeerlist:”0.us.pool.ntp.org 1.us.pool.ntp.org 2.us.pool.ntp.org 3.us.pool.ntp.org” /syncfromflags:manual /reliable:YES /update
– Execute the following command to actually perform a time synchronization with the external source
w32tm.exe /config /update
 
– Execute the following command for the changes to take effect(only from powershell)
Restart-Service w32time 
That’s it !!!!!!!