Skip to main content    

An official website of the United States government

Here’s how you know

**Official websites use .gov**              A **.gov** website belongs to an official government organization in the United States.            

**Secure .gov websites use HTTPS**              A **lock** (  LockA locked padlock) or **https://** means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.            

https://www.nist.gov/image/redefinition-second

            -  Topics  -  All Topics 
-  Advanced communications 
-  Artificial intelligence 
-  Bioscience 
-  Buildings and construction 
-  Chemistry 
-  Climate 
-  Cybersecurity 
-  Electronics 
-  Energy 
-  Environment 
-  Fire 
-  Forensic science 
-  Health 
-  Information technology 
-  Infrastructure 
-  Manufacturing 
-  Materials 
-  Mathematics and statistics 
-  Metrology 
-  Nanotechnology 
-  Neutron research 
-  Performance excellence 
-  Physics 
-  Public safety 
-  Resilience 
-  Standards 
-  Transportation 
 
            -  Publications 
            -  Labs & Major Programs  -  Laboratories    -  Communications Technology Laboratory 
  -  Engineering Laboratory 
  -  Information Technology Laboratory 
  -  Material Measurement Laboratory 
  -  Physical Measurement Laboratory 
-  User Facilities    -  NIST Center for Neutron Research 
  -  CNST NanoFab 
-  Research Test Beds 
-  Research Projects 
-  Tools & Instruments 
-  Major Programs    -  Baldrige Performance Excellence Program 
  -  CHIPS for America Initiative 
  -  Manufacturing Extension Partnership (MEP) 
  -  Office of Advanced Manufacturing 
  -  Special Programs Office 
  -  Technology Partnerships Office 
 
            -  Services & Resources  -  Standards and Measurements    -  Calibration Services 
  -  Laboratory Accreditation (NVLAP) 
  -  Quality System 
  -  Standard Reference Materials (SRMs) 
  -  Standards.gov 
  -  Time Services 
  -  Office of Weights and Measures 
-  Software 
-  Data    -  Chemistry WebBook 
  -  National Vulnerability Database 
  -  Physical Reference Data 
  -  Standard Reference Data (SRD) 
-  Storefront 
-  License & Patents 
-  Computer Security Resource Center (CSRC) 
-  NIST Research Library 
 
            -  News & Events  -  News 
-  Events 
-  Blogs 
-  Feature Stories 
-  Awards 
-  Video Gallery 
-  Image Gallery 
-  Media Contacts 
 
            -  About NIST  -  About Us    -  Leadership 
  -  Organization Structure 
  -  Budget & Planning 
-  Contact Us 
-  Visit 
-  Careers    -  Student programs 
-  Work with NIST 
-  History    -  NIST Digital Archives 
  -  NIST Museum 
  -  NIST and the Nobel 
-  Educational Resources 
 

IMAGES

## Share

Facebook

Linkedin

Twitter

Email

# Redefinition of the second

## Appears In

                        - Think You Know What a Second Is? It Will Likely Change in the Next Decade.

The definition of a second will change in the coming years. The good news is you’re unlikely to notice; it’ll just be more precise than before.

Download full image

### HEADQUARTERS

301-975-2000

Webmaster | Contact Us | Our Other Offices

TwitterFacebookLinkedInInstagramYouTubeGiphyRSS FeedMailing List

Feedback

            -  Site Privacy 
            -  Accessibility 
            -  Privacy Program 
            -  Copyrights 
            -  Vulnerability Disclosure 
            -  No Fear Act Policy 
            -  FOIA 
            -  Environmental Policy 
            -  Scientific Integrity 
            -  Information Quality Standards 
            -  Commerce.gov 
            -  Science.gov 
            -  USA.gov 
            -  Vote.gov