Users can find the current official date and time at Time.gov. A cooperative effort by the National Institute of Standards and Technology and the U.S. Naval Observatory provide this official time.
The time displayed at Time.gov does not vary by more than 0.0000001 seconds from Coordinated Universal Time, and the website corrects it to account for the delay in sending the signal through the Internet to the user's computer. It is the job of both the NIST and the USNO to maintain extremely accurate timekeeping devices, and both are sources of the official time for the United States. Civilian applications normally use NIST time, and military application typically use USNO time. These times never vary from each other by more than 20 nanoseconds.