Official U.S. Time Clock for all U.S. time zones provided by the two time agencies of the United States: a civilian agency, the National Institute of Standards and Technology (NIST) ...
http://www.time.gov/
AtomicClock Time Includes text and graphic representations of the atomicclock.
http://www.atomictime.net/
World Time Server Internet time clock with adjustments for Daylight Savings Time and global location choices.
http://www.worldtimeserver.com/
What Time Is It? Current time, from the U.S. Naval Observatory Master Clock.
Atomicclock - Wikipedia, the free encyclopedia NIST-F1 Caesium fountain atomicclock, serving as the US time and frequency ... The first accurate atomicclock, a caesium standard based on a certain ...