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NIST Internet Time Servers
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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.
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.
Name IP Address Location Status
nist1.uccaribe.edu 200.50.25.62 Bayamon, Puerto Rico Ok
nist1-ny.WiTime.net 64.90.182.55 New York City, NY Recommended for new users, new domain=ustiming.org, new ip=208.184.49.9
time-a.nist.gov 129.6.15.28 NIST, Gaithersburg, Maryland Ok
time-b.nist.gov 129.6.15.29 NIST, Gaithersburg, Maryland Ok
nist1-dc.WiTime.net 206.246.118.250 Alexandria, Virginia Recommended for new users, new domain=ustiming.org, new ip=206.246.118.250
nist1.aol-va.symmetricom.com 64.236.96.53 Reston, Virginia Recommended for new users
nist1.columbiacountyga.gov 68.216.79.113 Columbia County, Georgia Recommended for new users
nist.expertsmi.com 99.150.184.201 Monroe, Michigan Recommended for new users
nist.netservicesgroup.com 64.113.32.5 Southfield, Michigan Recommended for new users
time-a.timefreq.bldrdoc.gov 132.163.4.101 NIST, Boulder, Colorado Ok
time-b.timefreq.bldrdoc.gov 132.163.4.102 NIST, Boulder, Colorado Very busy
time-c.timefreq.bldrdoc.gov 132.163.4.103 NIST, Boulder, Colorado Ok
time.nist.gov 192.43.244.18 NCAR, Boulder, Colorado Ok
utcnist.colorado.edu 128.138.140.44 University of Colorado, Boulder ok
utcnist2.colorado.edu 128.138.188.172 University of Colorado, Boulder Recommended for new users
ntp-nist.ldsbc.edu 198.60.73.8 LDSBC, Salt Lake City, Utah Recommended for new users
time-nw.nist.gov 131.107.13.100 Microsoft, Redmond, Washington ok
nist1.aol-ca.symmetricom.com 207.200.81.113 Mountain View, California Recommended for new users
nist1.symmetricom.com 69.25.96.13 San Jose, California Recommended for new users
nist1-sj.WiTime.net 64.125.78.85 San Jose, California Recommended for new users, new domain=ustiming.org, new ip=64.125.78.85
nist1-la.WiTime.net 64.147.116.229 Los Angeles, California Recommended for new users, new domain= ustiming.org
The following server supports only authenticated NTP requests using the symmetric key encryption method that is defined in the NTP documentation. It does 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 this system; it will not respond to NTP requests from users who have not registered with NIST. This service is currently being offered on a trial basis only. See the authenticated NTP description for more information.
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