National Institute of of Standards & Technology
Maintains the standard for frequency and time interval for the United States, provides official time to the United States, Information about Radio controlled clocks, etc., located in Boulder, Colorado at the NIST Boulder Laboratories
U.S. Naval Observatory
One of the oldest scientific agencies in the country. Established in 1830 as the Depot of Charts and Instruments, its primary mission was to care for the U.S. Navy's chronometers, charts and other navigational equipment .
The Official U.S. Time
This public service is cooperatively provided by the two time agencies of United States: a Department of Commerce agency, the National Institute of Standards and Technology (NIST), and its military counterpart, the U. S. Naval Observatory (USNO). Readings from the clocks of these agencies contribute to world time, called Coordinated Universal Time (UTC). The time maintained by both agencies should never differ by more than 0.000 0001 seconds from UTC.
World Time Zones
Check time Zones around the world.