Explanation – Quartz clocks are accurate to within a few seconds per month, relying on the consistent oscillation of a quartz crystal. Atomic clocks, on the other hand, are far more accurate and precise, with deviations of only a few billionths of a second per day. Atomic clocks use the vibrations of atoms (such as cesium or hydrogen) to keep time, which provides a much higher level of accuracy and stability.

Source: The Hindu