1500 BCE
Egyptian sundials & shadow clocks
Egypt divides daylight using shadow-casting obelisks and sundials. Source — Wikipedia:
Chronological Storyline (10 Milestones)
250 BCE
Ctesibius’ precision water clock
Greek inventor Ctesibius builds accurate water clocks (clepsydrae) in Alexandria. Source — Wikipedia:
725 CE
Yi Xing’s escapement clock
Tang-dynasty monk Yi Xing and Liang Lingzan build a water-driven clock with an early escapement. Source — Wikipedia:
1088 CE
Su Song’s astronomical clock
Su Song’s towering Chinese clock couples an escapement to gear-trains and an armillary sphere. Source — Wikipedia:
1300 CE
Mechanical verge escapement
European monasteries adopt weight-driven mechanical clocks using the verge-and-foliot escapement. Source — Wikipedia:
1656 CE
Huygens’ pendulum clock
Christiaan Huygens’ pendulum clock improves accuracy from minutes to seconds per day. Source — Wikipedia:
1761 CE
Harrison’s marine chronometer
John Harrison’s H4 keeps time at sea accurately enough to solve the longitude problem. Source — Wikipedia:
1927 CE
Quartz clock
The quartz oscillator clock far surpasses mechanical timekeeping in stability. Source — Wikipedia:
1955 CE
Caesium atomic clock
Louis Essen’s caesium clock defines the second with unprecedented precision. Source — Wikipedia:
1985 CE
Network Time Protocol (NTP)
David Mills’ NTP synchronises clocks across the Internet to within milliseconds. Source — Wikipedia: