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 (ante meridian) and PM (post meridian) originated with the Romans.[1, p.33]

Today, time is popularly reckoned by caesium-atomic timekeeping. Prior to this, the most popular way to reckon time was by the motion of the celestial bodies.[4, p.66]

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


c.28,000 BCE: The reportedly earliest known example of something like a calendar was created by decorating a flat bone with circles and crescents. It was found in the Dordogne in France and the designs possibly depict moon phases.[4, p.67]

5th Millennium BCE: This is the earliest period to which devices created to mark the horizon have been dated. These devices have been found in megalithic sites.[4, p.67]

4900-4600 BCE: Among those megalithic sites are hundreds of stone circles found throughout central Europe. These were constructed with knowledge of the movements of the sky only attainable through observation and they served to assist with timekeeping.[1, p.12]

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

c.2500 BCE: The Sumerians detailed their accounts with day, month, and year.[6, p.22]

c.2400 BCE: The Sumerians were practicing intercalation.[6, p.22]

c.2100 BCE: The days was split into 24 hours by Egyptian priests. Ten of these were daylight, 2 were twilight, and 12 were night.[6, p.14]

c.1800 BCE: Egyptians priests made use of the star-clock.[6, p.15]

c.1700: Hammurabi ordered for an intercalation of their calendar.[6, p.22]

c.1600: This is the time in which the earliest known water-clock was created. It was found in Egypt.[6, p.15]

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

c.1450: This is the time in which the earliest known shadow-clock was created. It was found in Egypt.[6, p.15]

c.1300: Egyptians split a day into 12 daylight hours and 12 night hours.[6, p.14]

c.1100: The Assyrians inherited their calendar from the Babylonians.[6, p.24]

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

600s BCE: The MUL.APIN tablet shows evidence of timekeeping practices.[5, p.25] Alcman is the first to mention four seasons.[6, p.52]

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]

432 BCE: Meton makes note of what is now known as the Metonic cycle.[6, p.29]

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]

293 BCE: The first Roman sundial was created.[6, p.15]

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], [3]

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.

[4] – Felipe Fernández-Armesto. “Out of Our Minds: What We Think and How We Came to Think It” (2019).

[5] – Hannah, Robert. Greek and Roman Calendars: Constructions of Time in the Classical World. Illustrated, Bloomsbury Publishing Plc, 2005. Accessed 23 Jan. 2021.

[6] – E. J. Bickerman. “Chronology of the Ancient World” (1968). Accessed 30 Jan. 2021.

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