Windows Time Service overview

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

Windows Time Service overview

Computers keep the time on their internal clocks, which allows them to perform any function that requires the date or time. However, for scheduling purposes, the clocks must be set to the correct date and time, and they must be synchronized with the other clocks in the network. Without some other method in place, these clocks must be set manually.

With time synchronization, computers set their clocks automatically to match another computer's clock. One computer maintains very accurate time, and then all other computers set their clocks to match that computer. In this way, you can set accurate time on all computers.

How Windows Time Service works

In the Windows Server 2003 family, Windows Time Service automatically synchronizes the local computer's time with other computers on the network. The time source for this synchronization varies, depending on whether the computer is joined to an Active Directory® domain or a workgroup.

When the computers are part of a workgroup, you must manually configure the time synchronization settings. One or more computers might be identified as a locally reliable time source by configuring Windows Time Service on those computers to use a known accurate time source, either by using special hardware or a time source available on the Internet. Then, all other workgroup computers can be configured manually to synchronize their time with these local time sources.

When the computers belong to an family Active Directory domain, Windows Time Service configures itself automatically, using Windows Time Service that is available on domain controllers. Windows Time Service configures a domain controller within its domain as a reliable time source and synchronizes itself periodically with this source. These settings can be modified or overwritten, depending on specific needs.

Benefits of Windows Time Service

To function correctly, a number of Windows Server 2003 family components rely on accurate and synchronized time. For example, without clocks that are synchronized to the correct time on all computers, the Kerberos V5 authentication protocol might falsely interpret logon requests as intrusion attempts and deny access to users.

Another important benefit of time synchronization is the ability to correlate events on different computers in an enterprise. With synchronized clocks on all of your computers, you ensure that you can correctly analyze events that happen in sequence on multiple computers for success or failure.