Clocks have come a long way in the past one thousand years. In 1088, the Chinese developed a water clock accurate to about 100 seconds a day.

In the 17th Century, pendulum clocks were accurate to about 10 seconds a day. By the 1930s, the most accurate clocks kept time to within a second over a three-day interval.

But it was with the introduction of atomic clocks, based on precisely measured microwaves emitted by specific atoms, that the precision of timekeeping became astronomical.

Atomic clock technology enabled scientists in 1967 to define the second as the period equal to 9,192,631,770 cycles of the radiation that corresponds to the transition between two energy levels of the ground state of the caesium-133 atom.

By 1995, the best atomic clocks were accurate to a second every 15 million years - and now they have become even better with the new NISTL timepiece.