The accuracy of atomic clocks varies and is constantly improving. With an expected error of only 1 second in about 100 million years, the NIST-F1 in Boulder, Colorado, is one of the world's most precise clocks.
It is called a caesium fountain clock where lasers concentrate the atoms into a cloud, cool them down, and then toss them upwards. This method slows the atoms down, allowing for a longer measurement period and a more precise approximation of the natural frequency of the atoms.
Scientists are currently developing a device that is even more accurate than the current atomic clocks. The optical atomic clock uses light in the visible spectrum to measure atomic oscillations. The resonance frequency of the light rays is about 50,000 times higher than that of microwave radiation, allowing for a more precise measurement. The expected deviation of the new optical clock is 1 second in 15 billion years.
Planet Earth is an exceptionally accurate timekeeper
Some 450 atomic clocks around the world contribute to the calculation of International Atomic Time (TAI), one of the time standards used to determine Coordinated Universal Time (UTC) and local times around the world.
Satellite navigation systems like GPS, GLONASS, and Galileo also rely on precise time measurements to calculate positions accurately.