National Institute of Standards and Technology (NIST)
Nist Physics Laboratory: A Walk Through Time
An illustrated history of timekeeping from ancient times to the present. Includes information on ancient calendars, early clocks, a revolution in timekeeping, world time scales and time zones, and the NIST standards.
Extreme Science
Extreme Science: What Is the Time?
Take a walk through time as Extreme Science explains time starting with ancient calendars and early clocks to how the National Institute of Standards and Technology uses time today.