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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. 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 |
| time-a.nist.gov |
129.6.15.28 |
NIST, Gaithersburg, Maryland |
| time-b.nist.gov |
129.6.15.29 |
NIST, Gaithersburg, Maryland |
| time-a.timefreq.bldrdoc.gov |
132.163.4.101 |
NIST, Boulder, Colorado |
| time-b.timefreq.bldrdoc.gov |
132.163.4.102 |
NIST, Boulder, Colorado |
| time-c.timefreq.bldrdoc.gov |
132.163.4.103 |
NIST, Boulder, Colorado |
| utcnist.colorado.edu |
128.138.140.44 |
University of Colorado, Boulder |
| time.nist.gov |
192.43.244.18 |
NCAR, Boulder, Colorado |
| time-nw.nist.gov |
131.107.13.100 |
Microsoft, Redmond, Washington |
| nist1.symmetricom.com |
69.25.96.13 |
Symmetricom, San Jose, California |
| nist1-dc.WiTime.net |
206.246.118.250 |
WiTime, Virginia |
| nist1-ny.WiTime.net |
208.184.49.9 |
WiTime, New York City |
| nist1-sj.WiTime.net |
64.125.78.85 |
WiTime, San Jose, California |
| nist1.aol-ca.symmetricom.com |
207.200.81.113 |
Symmetricom, AOL facility, Sunnyvale, California |
| nist1.aol-va.symmetricom.com |
64.236.96.53 |
Symmetricom, AOL facility, Virginia |
| nist1.columbiacountyga.gov |
68.216.79.113 |
Columbia County, Georgia |
| nist.expertsmi.com |
71.13.91.122 |
Monroe, Michigan |
| nist.netservicesgroup.com |
64.113.32.5 |
Southfield, Michigan |
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.
| ntp-a.boulder.nist.gov |
132.163.4.107 |
NIST, Boulder, Colorado |
Because requests for NIST Internet Time Service continue to rapidly grow, we are always interested in the possibility of expanding the number of servers and broadening their geographic distribution. All organizations interested in possibly hosting a NIST Internet Time Service server are invited to contact Time and Frequency Division Chief Thomas O'Brian for more information, including a description of the equipment that the organization must have available and a discussion of the other technical qualifications necessary to host a server:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
. NIST does not charge the hosting organization for this service.
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