Modern clock

Some modern stationary and watches are still manufactured with mechanical drive, however the electric and electronic watches have become the norm. In many electric clock move arrows provides a motor which works on AC current with frequency of 50-60 Hz. A similar principle of work and some digital electronic clock, but they show the time on a digital light Board. The electronic wristwatch needs its own regulator, and this role often plays the quartz crystal which provides a nearly constant frequency of vibration under the action of electricity. The vibrating crystal generates precise time the electrical impulses that control the display of electronic figures or movement of mechanical arrows. Most inpatient hours also work on quartz crystals.
Quartz watch gives a very high accuracy up to 1 /30 seconds per day, but that's yesterday's news compared to atomic clocks that use the frequency of radiation of atoms of some elements (e.g., cesium) and provide an electronic indication of time with an error of less than one second per thousand years. Such clocks are used in experiments that require accurate timing, and to determine the time: today the second is defined as the length of time for which an atom of cesium-133 emit of 9 192 631 770 impulses to certain specific conditions.