Something many of us are probably not aware of is that some of our clocks actually rely on the electric power grid in order to regulate themselves. Cell phones and computers are directly connected to the atomic-clock regulated internet time signal, but other clocks – some plug-in electric clocks, as well as many appliance clocks – rely on the frequency of AC power delivered by generating stations. Generally, the frequency of the grid is 50 or 60 Hz, depending on where you are, and the stability of the grid's frequency is used to correct the time in clocks getting energy from mains, rather than batteries. This is thanks to a synchronous electric motor (these were first invented in 1926, and the inventor, Laurens Hammond, gave away many clocks to power station operators, to encourage them to keep the grid frequency stable).
Time error correction from the grid is still used in many electric and appliance clocks, and recently, in Europe, a dispute between Kosovo and Serbia let to a deviation in frequency in the European power grid, resulting in what you might call a non-trivial error in grid-regulated clocks.