NIST Internet Time Servers
|Return to NIST Internet Time Service Page
The table below lists the time servers used by the NIST Internet Time Service (ITS). The table lists each server's name, IP address, and location, organized geographically within the US from North to South and then from East to West. Please note that while we make every effort to ensure that the names of the servers are correct, we control the names of only the nist.gov servers. If you have difficulty using the name of a system, you can access a server using the IP address directly.Important notes:
The global address time.nist.gov is resolved to all of the server addresses below in a round-robin sequence to equalize the load across all of the servers.
Whether you connect to a server using the name or the IP address, it is a bad practice to “hard-code” a particular server name or address into a device so that these parameters cannot be changed by the end user if that becomes necessary at some future time.
All users should ensure that their software NEVER queries a server more frequently than once every 4 seconds. Systems that exceed this rate will be refused service. In extreme cases, systems that exceed this limit may be considered as attempting a denial-of-service attack.
|time-a-g.nist.gov||220.127.116.11||NIST, Gaithersburg, Maryland||all services ok|
|time-b-g.nist.gov||18.104.22.168||NIST, Gaithersburg, Maryland||All services ok|
|time-c-g.nist.gov||22.214.171.124||NIST, Gaithersburg, Maryland||All services available|
|time-d-g.nist.gov||126.96.36.199||NIST, Gaithersburg, Maryland||All services available|
|time-d-g.nist.gov||2610:20:6F15:15::27||NIST, Gaithersburg, Maryland||All services via IPV6|
|time-a-wwv.nist.gov||188.8.131.52||WWV, Fort Collins, Colorado||All services available|
|time-b-wwv.nist.gov||184.108.40.206||WWV, Fort Collins, Colorado||All services avaiable|
|time-c-wwv.nist.gov||220.127.116.11||WWV, Fort Collins, Colorado||All services available|
|time-d-wwv.nist.gov||18.104.22.168||WWV, Fort Collins, Colorado||All services available|
|time-d-wwv.nist.gov||2610:20:6f97:97::4||WWV, Fort Collins, Colorado||All services via IPv6|
|time-a-b.nist.gov||22.214.171.124||NIST, Boulder, Colorado||All services available|
|time-b-b.nist.gov||126.96.36.199||NIST, Boulder, Colorado||All services available|
|time-c-b.nist.gov||188.8.131.52||NIST, Boulder, Colorado||All services available|
|time-d-b.nist.gov||184.108.40.206||NIST, Boulder, Colorado||All services available|
|time-d-b.nist.gov||2610:20:6f96:96::4||NIST, Boulder, Colorado||Services via IPv6|
|time.nist.gov||global address for all servers||Multiple locations||All services available|
|utcnist.colorado.edu||220.127.116.11||University of Colorado, Boulder||All services available|
|utcnist2.colorado.edu||18.104.22.168||University of Colorado, Boulder||All services available|
The following servers support only authenticated NTP requests using the symmetric key encryption method that is defined in the NTP documentation. They do not respond to requests for time in the DAYTIME or TIME formats and will not accept anonymous ftp connections. You must apply to NIST for an encryption key to use these systems; they will not respond to NTP requests from users who have not registered with NIST. See the authenticated NTP description for more information.
|ntp-b.nist.gov||22.214.171.124||NIST, Boulder, Colorado||Authenticated service|
|ntp-wwv.nist.gov||126.96.36.199||NIST WWV, Fort Collins, Colorado||Authenticated service|
|ntp-c.colorado.edu||188.8.131.52||JILA, Univ. of Colorado, Boulder||Authenticated Service|
|ntp-d.nist.gov||184.108.40.206||NIST, Gaithersburg, Maryland||Authenticated Service|
The following server supports only the NTP format and transmits UT1 time rather than UTC(NIST). For details about the UT1 server, please see the UT1 NTP Information page.
|ut1-time.colorado.edu||220.127.116.11||University of Colorado, Boulder|