Time synchronization in Windows 10 and Windows Server 2016 has been substantially improved. Under reasonable operating conditions, systems can be configured to maintain 1 ms (millisecond) accuracy or better (with respect to UTC).
Warning
Windows Server 2012 R2 and below can not meet the same high accuracy objectives. These operating systems are not supported for high accuracy. In these versions, the Windows Time service satisfied the following requirements:
Provided the necessary time accuracy to satisfy Kerberos version 5 authentication requirements.
Provided loosely accurate time for Windows clients and servers joined to a common Active Directory forest.
Greater tolerances on 2012 R2 and below are outside the design specification of the Windows Time service.
Windows 10 and Windows Server 2016 default configuration
While we support accuracy up to 1 ms on Windows 10 or Windows Server 2016, most customers don't require highly accurate time.
As such, the default configuration is intended to satisfy the same requirements as prior operating systems that:
Provide the necessary time accuracy to satisfy Kerberos version 5 authentication requirements.
Provide loosely accurate time for Windows clients and servers joined to a common Active Directory forest.
How to configure systems for high accuracy
Time accuracy entails the end-to-end distribution of accurate time from the authoritative time source to the end device. Anything that adds asymmetry in measurements along this path will negatively influence the accuracy achievable on your devices.
High accuracy configurations require Windows 10 or Windows Server 2016. All Windows devices in the time topology must meet this requirement including higher stratum Windows time servers, and in virtualized scenarios, the Hyper-V Hosts that run the time-sensitive virtual machines. All of these devices must be at least Windows 10 or Windows Server 2016.
In the illustration shown below, the virtual machines requiring high accuracy are running Windows 10 or Windows Server 2016. Likewise, the Hyper-V Host on which the virtual machines reside, and the upstream Windows time server must also run Windows Server 2016.
Tip
You can run the command winver at a command prompt to verify the OS version is 1607 (or higher) and OS Build is 14393 (or higher) as shown below:
System configuration
Reaching high accuracy targets requires system configuration. There are various ways to perform this configuration, including directly in the registry or through group policy. More information for each of these settings can be found in the Windows Time Service Technical Reference: Windows Time Service Tools.
Windows Time service startup type
The Windows Time service (W32Time) must run continuously. To do this, configure the Windows Time service's startup type to "Automatic" start.
To calculate the cumulative one-way network latency, add the individual one-way delays between pairs of NTP client-server nodes in the time topology, starting with the target and ending at the high-accuracy stratum 1 time source.
For example: Consider a time sync hierarchy with a highly accurate source, two intermediary NTP servers A and B, and the target machine in that order. To obtain the cumulative network latency between the target and source, measure the average individual NTP roundtrip times (RTTs) between:
The target and time server B
Time server B and time server A
Time server A and the Source
This measurement can be obtained using the inbox w32tm.exe tool. To do this:
Perform the calculation from the target and time server B.
As a Windows Server hybrid administrator, you integrate Windows Server environments with Azure services and manage Windows Server in on-premises networks.
Time synchronization accuracy in Windows Server 2016 has been improved substantially, while maintaining full backwards NTP compatibility with older Windows versions.
The W32Time service provides network clock synchronization for computers without the need for extensive configuration. The W32Time service is essential to the successful operation of Kerberos V5 authentication and, therefore, to AD DS-based authentication.
Windows Server 2016 time accuracy has been improved. These updates are targeted to meet accuracy regulations in the US and EU. Learn about the improvements and how to achieve this benefit in your environment. For more detailed information see https://aka.ms/WS2016Time