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5000 BCE
Early humans use circadian rhythm
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3000 BCE
Egyptians use the obelisk to tell time.
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3000 BCE
Early Greeks and Egyptians design a water clock.
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300 BCE
Babylonians use the sundial to tell time.
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1100
The hourglass used in Europe
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1300
Mechanical clocks representing a 12-hour period in Europe.
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1400
Watches or timepieces portable time. Appeared first in Italy.
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1500
Nicolas Copernicus' philosophy that sun revolves around sun annually and every 24 hours on its own axis