This article describes the Simple Network Time Protocol
(SNTP) time servers that are available on the Internet.
There are two levels, or tiers, of Network Time Protocol
(NTP) time servers that are available on the Internet. The NTP is defined in
Request for Comments (RFC) 1305.
The first-level time servers are
primarily intended to act as source time servers for second-level time servers.
The first-level time servers may also be capable of providing mission-critical
time services. Some first-level time servers may have a restricted access
Second-level time servers are intended for general SNTP time
service needs. Second-level time servers usually enable public access. It is
recommended that you use second-level time servers for normal SNTP time server
configuration because they are usually located on a closer network that can
produce faster updates.
It is recommended that you research any time
server selection to ensure that it can meet your specific time server
Time server listNote
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Microsoft does not maintain the list of time servers or recommend one time server over the other one. These links are for your reference and research to select the time server(s) appropriate for your configuration. Microsoft does recommend that workgroup computers sync from the Microsoft NTP server (time.windows.com). If another time source is desired, we recommend that you use one of the Stratum 2 Time Servers. To find the Stratum 2 Time Servers that are available, visit the following Web site: Note
Please read the "Rules Of Engagement" before using the Stratum Two Time Servers list. To read the "Rules of Engagement," visit the following Web site:
Domain joined member computers and application servers should be configured to synchronize time by using the domain hierarchy as described in the Domain Hierarchy-Based Synchronization
topic at the following Microsoft TechNet Web site:
To synchronize non-domain-joined (workgroup) workstations or servers, visit the following Microsoft TechNet Web site:
For more information about the use of time services in Windows Server and Windows NT, click the following article numbers to view the articles in the Microsoft Knowledge Base:
Considerations when hosting Active Directory domain controller in virtual hosting environments
"Could Not Locate a Time Server" After Setting SNTP Time Server Using NET TIME Command
How to configure an authoritative time server in Windows 2000
Basic Operation of the Windows Time Service
The W32Time service does not synchronize the CMOS clock time to the Internet time on a Windows XP or Windows Server 2003-based computer after the W32Time service stops
How to detect and recover from a USN rollback in Windows Server 2003
Support boundary to configure the Windows Time service for high accuracy environments
Support policy for Microsoft software running in non-Microsoft hardware virtualization software
Advancing time on production computers and the effect on Active Directory and FRS