The 'leap second' is no more. How a minor time adjustment became a major problem

For more than 50 years, humanity has used "leap seconds" to keep our clocks aligned with the rotation of the Earth.

On Thursday, an international time-keeping body in France is expected to do away with leap seconds and let the clocks slip until they're out of alignment by a full hour — meaning it could be centuries, or even millennia, before another tweak is needed.