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This web site is a public service of the NIST Time and Frequency Division, an operating unit of the Physical Measurement Laboratory of the National Institute of Standards and Technology (NIST).

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You may link to any portion of this site, as long as your link does not imply endorsement by NIST.


General disclaimer

While we make every effort to verify information on this web site, there may occasionally be technical inaccuracies or typographical errors. Information may be changed or updated without notice.

NIST strives to deliver a high quality information service and to verify that the content on this site is technically accurate. However, NIST makes no warranties to that effect, and NIST shall not be liable for any damage that may result from errors or omissions in the web site.

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Many aspects of NIST's time signal services require third-party organizations to produce hardware and software applications for the public. Throughout this site, links to external web sites are available and have been clearly noted. The companies and sites identified are provided in order to assist users of NIST services, but keep in mind that NIST does not make endorsements of commercial products. In no case does identification of a product or company on this site imply recommendation, endorsement, or certification by NIST.


This web site serves the American public and most of it is not copyrighted. However, you may not reproduce any portions of this site for commercial gains. Moreover, if you wish to reproduce any portion of this site that we have licensed from other parties, you must contact the other parties to obtain reproduction rights.

Created January 12, 2010, Updated August 25, 2016