Atomic clocks are incredibly precise and accurate timekeeping devices. The accuracy of an atomic clock is generally measured in terms of its frequency stability, which refers to how well it maintains a constant frequency over time. The frequency stability of atomic clocks is typically expressed in terms of fractional frequency instability, which is the ratio of the frequency drift to the nominal frequency of the clock.

For example, if an atomic clock has a fractional frequency instability of 1 x 10^-15, it means that its frequency may drift by 1 second every 100 billion seconds. Over 1.7 million years (approximately 5.3 x 10^11 seconds), such an atomic clock would accumulate a time error of only about 0.053 seconds.

It's worth noting that this calculation assumes a constant frequency instability over the entire 1.7 million years, which may not be the case in reality. However, atomic clocks are designed and maintained to minimize frequency drift and maintain exceptional accuracy over long periods of time.

Atomic clocks play a crucial role in various scientific research and applications, including navigation systems, telecommunications, and synchronization of global networks, where precise timing is essential.