The first accurate atomic clock was built in 1955. This led to the internationally agreed definition of the second being based on atomic time.

Under the International System of Units, the second is currently defined as the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium atom.

Feel the rhythm of the Universe's symphony with the Atomic Clock screensaver and always know the accurate time!

• Atomic Clock ScreenSaver 2.5
  The first accurate atomic clock was built in 1955. This led to the internationally agreed definition of the second being based on atomic time. Under the International...

• Vista Clock 1.1
  Vista Clock - put on your desktop a stylish free analog/digital clock with Countdown, Chimes, Timer, Uptime, Stopwatch, World Clock, Atomic Clock and Skins

• Skins Pack for Atomic Alarm Clock 1.1
  Additional skins pack for Atomic Alarm Clock. Alert yourself about important events with different alarms and replace your computer tray clock using different skins. Computer Alarm Clock that will play any MP3 file. It can also run a program, log...

• Desktop Atomic Clock 2.23
  Desktop Atomic Clock is a program to synchronize your computer clock with an atomic clock over the Internet

• On-Time Atomic Clock Sync 2.0
  Synchronize your PC's clock with internet atomic clock servers

• Atomic Time Synchronizer 5.5.10
  Atomic Time Synchronizer is a useful and handy utility to keep your PC clock accurate

• Li'l Atomic Clock 1.0.1
  Synchronizes the system time with atomic clock driven NTP-servers in internet