USNO NTP Network Time Servers

The Naval Observatory operates an ensemble of stratum 1 NTP servers which are synchronized to the USNO Master Clocks or to GPS as their stratum 0 reference clocks.

USNO NTP Servers in the United States

Network Time Protocol (NTP) is an Internet standard protocol which enables client computers to maintain system time synchronization to the US Naval Observatory Master Clocks in Washington, DC and Colorado Springs, CO.

NTP runs as a client program on a computer. It sends periodic time requests to one or more servers, obtaining server time stamps and using them to adjust the client's clock.

Typical accuracy achieved is in the range 1 - 30 ms continuous, and is highly dependent on the symmetry and speed of the Internet path between client and server. Best results are achieved using a combination of servers which are closest to the client in a network sense.

To obtain precise time from USNO NTP servers, follow these procedures:

  1. Download NTP client software from ntp.org.
  2. Select several NTP servers and add to your client configuration.
  3. Run the NTP client on your machine.

We request that you allow no more than three of your clients to poll our servers directly. Organizations with many clients should obtain time from local stratum 2 servers. ISPs should configure routers or firewalls to serve as stratum 2 servers to the ISP network. Dialin clients should contact your ISP for information about NTP services.

All of the following stratum 1 NTP servers are open to stratum 2 servers within the same time zone and to others by arrangement. Individual users should consult the public list of stratum 2 servers.

Please note that these servers support only Network Time Protocol (IETF RFC-1305/ RFC-5905) and Simple Network Time Protocol (SNTP).

WE STRONGLY RECOMMEND THAT YOU CHOOSE ONE OR MORE SERVERS CLOSE TO YOU, AND IN ADDITION SELECT OTHER SERVERS FOR REDUNDANCY.


U.S. Eastern Time Zone

  • tick.usno.navy.mil
  • Location: Time Service Dept., U.S. Naval Observatory, Washington, DC
    Synchronization: NTP V4 primary (USNO Master Clock H-masers)
    Access Policy: open access for MIL, GOV, and other stratum 2 servers.
    Note, USNO operates three NTP servers at this address as part of a load-balanced farm to handle high traffic.

  • ntp-s1.cise.ufl.edu
  • Location: University of Florida, Gainesville, FL
    Synchronization: NTP V4 primary
    Access Policy: open access for stratum 2 servers and UFL clients,others by arrangement

  • ntp.colby.edu
  • Location: Colby College, Waterville, ME
    Synchronization: NTP V4 primary
    Access Policy: open access for stratum 2 servers and Colby clients,others by arrangement

  • navobs1.oar.net
  • Location: OARnet, Ohio State University, Columbus, Ohio
    Synchronization: NTP V4 primary
    Access Policy: open access for stratum 2 servers and OARnet, others by arrangement

  • gnomon.cc.columbia.edu
  • Location: Columbia University, New York City
    Synchronization: NTP V4 primary
    Access Policy: open access for stratum 2 servers and CU, others by arrangement

  • tick.gatech.edu
  • Location: Georgia Institute of Technology, Atlanta, Georgia
    Synchronization: NTP V4 primary
    Access Policy: open access for stratum 2 servers and GATECH clients, others by arrangement

    U.S. Central Time Zone

  • ntp.okstate.edu
  • Location: Oklahoma State University, Stillwater, OK
    Synchronization: NTP V4 primary
    Access Policy: open access for Central and neighboring time zones, others by arrangement

  • navobs1.wustl.edu
  • Location: Washington University, St. Louis, Missouri
    Synchronization: NTP V4 primary
    Access Policy: open access for stratum 2 servers and WUSTL, others by arrangement

  • tick.uh.edu
  • Location: University of Houston, Houston, Texas
    Access Policy: open access for stratum 2 servers and UH, others by arrangement

    U.S. Mountain Time Zone

  • tick.usnogps.navy.mil
  • Location: US Naval Observatory Alternate Master Clock, Colorado Springs, CO
    Synchronization: NTP V4 primary (USNO Master Clock H-masers)
    Access Policy: open access for MIL, GOV, and stratum 2 servers, others by arrangement

    U.S. Pacific Time Zone

  • montpelier.caltech.edu
  • Location: California Institute of Technology, Pasadena, CA
    Synchronization: NTP V4 primary
    Access Policy: open access for stratum 2 servers and Caltech clients, others by arrangement

  • bigben.cac.washington.edu
  • Location: University of Washington, Seattle, Washington
    Synchronization: NTP V4 primary
    Access Policy: open access for stratum 2 servers and UW clients, others by arrangement

  • tick.ucla.edu
  • Location: University of California, Los Angeles
    Synchronization: NTP V4 primary
    Access Policy: open access for stratum 2 servers and UCLA clients; others by arrangement

  • usno.pa-x.dec.com
  • Location: Compaq Corporation, Palo Alto, CA
    Synchronization: NTP V4 primary
    Access Policy: open access for stratum 2 servers, Compaq, others by arrangement

    Alaska Time Zone

  • ntp.alaska.edu
  • Location: University of Alaska, Fairbanks, AK
    Access Policy: open access for stratum 2 servers and UAF, others by arrangement



    For further information contact
    Time Service Dept., USNO

    Back to Time Service Home Page
    "The inaudible and noiseless foot of Time." --W. S.