Windows Time synchronization is often a mystery. Like many processes we are only forced to learn about it when it does not function as we expect. By design each client computer in a domain receives its time from a Domain Controller. Domain Controllers sync their time from the Domain’s PDC Operation Master. It is therefore essential that the PDC time is correct. In order to assure the accuracy of this time we will sync the PDC to an external time source.

There are many NTP (Network Time Protocol) sources available on the internet. Pool.NTP.ORG uses DNS round robin to make a random selection from a pool of time servers who have volunteered to be in the pool. Currently over 3500 NTP servers are included in the pool. NTP uses UDP port 123 by default, remember to check your firewall policy to assure the sync works.

Below we will link our PDC to the external servers.

1.First, locate your PDC Server. Open the command prompt and type:

netdom /query fsmo

2.Log in to your PDC Server and open the command prompt.


3.Stop the W32Time service:

net stop w32time

4.Configure the external time sources, type:

w32tm /config /syncfromflags:manual /,,,

5.Make your PDC a reliable time source for the clients. Type:

w32tm /config /reliable:yes

6.Start the w32time service:

net start w32time

7.The windows time service should begin synchronizing the time. You can check the external NTP servers in the time configuration by typing:

w32tm /query /configuration

8.Check the Event Viewer (System) for any errors.

Windows schedules the synchronizations for each Sunday at 1 am by default. Next time we will discuss how to enact a schedule to update more frequently.


For more information about this or any other subject please contact

-Eric Thompson

-ALI Technical Assistance Center

(800) 283-2648 option 2