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Around 3000 BCE Egyptians told time by the shadow cast by by an obelisk.
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Although it is difficult to establish a date, the ancient Chinese were using knotted rope burning at intervals to tell time by the time there were written records in 1700 BCE.
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Early Greeks and Egyptians used water to tell time when the sun wasn't available. These water clocks were called clepsydras and were made of bowls with water slowly flowing from one to another. Time was measured by lines marking the water levels.
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Around 300 BCE sundials were used in Babylonia on a flat circle representing a 12-hour clock.
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The origin of the hourglass is unclear but some experts believe it was invented in Alexandria around 150 BCE. The hourglass was a portable way to tell time.
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Notched graduated candles used to determine time were first mentioned in a Chinese poem around 520 CE.
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By using weights and balances mechanical clocks marked increments of time measured out over a 12 hour period. They were first invented in Europe in 1300 CE. They were rather large and did not keep accurate time.
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Wearable timepieces appeared around 1400 in Italy. The watches measured time with coiled springs. Improvements lead to smaller and more accurate timepieces.
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A pendulum clock used a swinging rod shaped weight for control. Pendulum clocks were much more accurate than their predecessors, and could measure minutes and seconds as well as hours.
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In 1969 quartz crystals were used instead of spring coils in clocks and watches. In modern times, most clocks and watches have quartz in them.
