The History of Timekeeping

“…timekeeping was critical to the birth of modern science…”[1, p.83]
Ken Mondschein (2020)

The practice of starting the day at midnight and splitting the day into AM and PM originated with the Romans.[1, p.33]

Some people have argued that Stonehenge is an example of an ancient timekeeping device. Same for Carahunge and Chanquillo.[1, p.12]


4900-4600 BCE: “…several hundred circular enclosures constructed in central Europe … were definitely aligned with calendar observations.”[1, p.12]

3500 BCE: The Egyptians used obelisks as timekeeping devices.[1, p.13]

By 1500 BCE: The Egyptians had sundials, merkhets, and water clocks.[1, p.13]

700s BCE: The MUL.APIN tablet shows evidence of timekeeping practices.[1, p.13]

After c.600 BCE: The Chinese started tracking time through a unit they called “qi”.[1, p.25] A qi divided the year starting in the winter solstice into 24 parts consisting of 15 days each. This made the year 360 days long.[2, p.888]

C6th BCE: The Chinese potentially had water clocks.[1, p.56]

C4th BCE: The Chinese astronomer Gan De organized the sky into 365.25 degrees.[1, p.19]

C3rd BCE: Romans didn’t care much for accurate timekeeping.[1, p.32]

C2nd BCE: Romans took more of an interest in accurate timekeeping.[1, p.32]

C1st BCE: The Antikythera Mechanism exists.[1, p.15]

c.550 CE: Zhang Zixin (張子信) commented that the speed of the sun across the sky fluctuated with the passing of the year.[1, p.25], [2, p.888]

1045 CE: The earliest known Latin writing on how to construct an astrolabe was written by the Benedictine monk Hermann from the abbey of Reichenau.[1, p.46]

1206 CE: Ismail al-Jazari described a number of clocks in his Book of Ingenious Devices.[1, p.50]

c.1300 CE: The mechanical clock with the ability to mark equal hours was invented.[1, p.42]

C14th CE: Charles V ordered the installation of the first public clocks in Paris. Also, the hourglass was invented.[1, p.47]

c.1430: The first spring-driven clocks were invented.[1, p.93]

1530: Gemma Frisius’ On the Principles of Astronomical Cosmography was the first to work to ever suggest determining longitude with the help of a clock.[1, p.115]

Early C17th CE: Galileo became the first known instance of a scientists employing a timekeeping device to assist in proving/disproving a hypothesis through experimentation.[1, p.77]

1656: Christiaan Huygens developed the first working pendulum clock.[1, p.86]

1684: The term chronometer was coined.[1, p.112]

1690s: The stopwatch was invented.[1, p.99]

1735: The chronometer was invented.[1, p.112]

1840: Standard time was first established.[1, p.139]

1895: The idea of Daylight Savings Time was first seriously proposed.[1, p.141]

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[1] – Mondschein, Ken, and Neal Stephenson. On Time: a History of Western Timekeeping. Johns Hopkins University Press, 2020.

[2] – Mitsuru Soma, Kin-aki Kawabata, and Tanikawa Kiyotaka. “Units of Time in Ancient China and Japan,” Publications of the Astronomical Society in Japan 56, no. 5 (October 25, 2004). Accessed 6 Jan. 2021.

[3] – Accessed 11 Jan. 2021.

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