Configure 2008 Server for an External Time Source

When running the 2008 R2 BPA for the Active Directoy role I got an error that the server wasn't configured to fetch time from an external time source.

In a nutshell run this command on the server that holds the PDC FSMO role:

w32tm /config /manualpeerlist:us.pool.ntp.org /syncfromflags:manual /reliable:yes /update

This sets the external time source to a pool of US servers hosted by NTP.org.

Note: A quick way to check the location of the FSMO roles: netdom /query fsmo

Reference

http://technet.microsoft.com/en-us/library/cc786897%28v=ws.10%29.aspx