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Huygens first used a clock to calculate the equation of time (the difference between the apparent solar time and the time given by a clock), publishing his results in 1665. The relationship enabled astronomers to use the stars to measure sidereal time , which provided an accurate method for setting clocks.
Electronic time clock. A time clock, sometimes known as a clock card machine, punch clock, or time recorder, is a device that records start and end times for hourly employees (or those on flexi-time) at a place of business. In mechanical time clocks, this was accomplished by inserting a heavy paper card, called a time card
An analog pendulum clock made around 18th century. A clock or chronometer is a device that measures and displays time.The clock is one of the oldest human inventions, meeting the need to measure intervals of time shorter than the natural units such as the day, the lunar month, and the year.
c. 3500 BC - Egyptian obelisks are among the earliest shadow clocks. [1] c. 1500 BC - The oldest of all known sundials, dating back to the 19th Dynasty. [2] c. 500 BC - A shadow clock is developed similar in shape to a bent T-square. [3] 3rd century BC - Berossos invents the hemispherical sundial. [4] 270 BCE - Ctesibius builds a water clock.
A pendulum clock is a clock that uses a pendulum, a swinging weight, as its timekeeping element. The advantage of a pendulum for timekeeping is that it is an approximate harmonic oscillator: It swings back and forth in a precise time interval dependent on its length, and resists swinging at other rates.
Digital clocks typically use the 50 or 60 hertz oscillation of AC power or a 32,768 hertz crystal oscillator as in a quartz clock to keep time. Most digital clocks display the hour of the day in 24-hour format; in the United States and a few other countries, a commonly used hour sequence option is 12-hour format (with some indication of AM or PM).