Configuring Time Service
By default, only the first domain controller or so-called Root domain controller and finally so-called "PDC Emulator" is configured to be a Reliable Time Source.
If it doesn't exist you need to create it to make it ReliableTimeSource for other client computers and domain controllers.
Let me explain something:
By default client machines use *default heirarchy" to synchronize time. Clients will only sync with their own domain controllers in the domain. This is default bahviour and by design and to keep time closer between all PCs.
PDC is the 2nd highest stratum. Client will try to sync time with their own domain controller *unless* specifically you specify to do so. Becuase PDC is configured an authoritative server by default. It is configured using *ReliableTimeSource" entry in registry.
1 External NTP time source
2 PDC emulator of the forest root domain
3 Domain controllers in the forest root domain or PDC emulators in child domains
4 Workstations and member servers in the forest root domain or domain controllers in child domains
5 Workstations and member servers in child domains
Computers choose a time source according to a specific order of preference. This order, from most preferred to least preferred. The following table displays the preferences for Selecting a Time Source:
Preference Computer Location Reliability of Time Source
1 Parent domain controller In-site Reliable
2 Local domain controller In-site Reliable
3 Parent domain controller In-site Not reliable
4 Local PDC emulator In-site Not reliable
5 Parent domain controller Out-of-site Reliable
6 Local domain controller Out-of-site Reliable
7 Parent domain controller Out-of-site Not reliable
8 Local PDC emulator Out-of-site Not reliable
There is nothing much you need to do with *ReliableTimeSource* entry in registry. Simply edit the value and set it to 1 to make it Reliable time source for all computers in your network.
Moreover, you can also configure your PDC or Root Domain Controller to sync with hardware as a source time server but it is recommended that you configure your PDC to sync with an external time source.
How to configure an Authoritative Time server in Windows 2000: