Clock guides · Clock history

Who invented the clock?

The honest answer is that nobody did, or rather that many people did, one step at a time. It depends on what you count as a clock.

By David Ray · Updated November 10, 2026

It depends what you call a clock

There is no single inventor of the clock. If a clock is anything that tells the time, the first ones were shadows. If it means a machine that keeps time by itself, it was a gradual invention of medieval Europe, and nobody knows who built the first. If it means an accurate clock, credit goes to Christiaan Huygens in 1656.

Each step solved a problem the last one could not: sundials stopped at night, water clocks were hard to keep steady, and early mechanical clocks drifted badly.

Shadows and the first sundials

NIST notes that Egyptian obelisks built as early as 3500 BCE cast moving shadows that divided the day into morning and afternoon. Britannica suggests a simple upright stick was probably the first time-telling device of all.

Sources disagree on the oldest surviving sundial. Royal Museums Greenwich dates the earliest known Egyptian example to at least 3,500 years ago, while Britannica names a green schist shadow clock from the 8th century BCE or earlier as the oldest preserved one.

Want the exact time right now? See it on a big, clean clock at OnlineClock.app, free, with no sign-up.

Water clocks: time after dark

A water clock measures time by a steady flow of water, so it works at night and under clouds. According to NIST, one of the oldest known was found in the tomb of the Egyptian pharaoh Amenhotep I, who was buried around 1500 BCE.

The Greek inventor Ctesibius of Alexandria improved them in the 3rd century BCE with a float that rose as water flowed in, carrying a pointer. In China, Su Song's astronomical clock tower of 1088 used a waterwheel that released its power in small regular steps, which the Science Museum in London describes as acting like an escapement.

See also: how sundials, water clocks and hourglasses worked on OnlineClock.app.

The first mechanical clocks

Nobody knows exactly where or when the first all-mechanical clock was made. Britannica says its origin is unknown and suggests the first ones may have been used in monasteries to ring a bell calling monks to prayer.

These clocks were driven by weights and controlled by the verge escapement, which Britannica says was probably invented in 13th-century Europe. NIST notes that large weight-driven clocks appeared in the towers of several big Italian cities in the first half of the 14th century. The oldest survivors, such as those at Salisbury and Wells cathedrals in England, carry no maker's name, and their exact dates are still argued over.

See also: the full story of the mechanical clock's invention on OnlineClock.app.

Huygens and the pendulum clock

The leap to accurate clocks came from the Dutch scientist Christiaan Huygens, who designed a pendulum clock in 1656. The Hague clockmaker Salomon Coster built it, and Guinness World Records dates the first working example to June 1657, which is why both years appear in histories.

Galileo had studied pendulums and sketched a pendulum clock, but NIST notes he died in 1642 without building one. Huygens's clock erred by less than a minute a day, a huge improvement, and pendulum clocks stayed the most accurate timekeepers for almost three centuries.

Quartz and atomic clocks

The first quartz clock was built in 1927 by Joseph W. Horton and Warren A. Marrison of Bell Laboratories, according to NIST. Some histories give 1928. Quartz reached the wrist with the Seiko Astron on 25 December 1969.

The first atomic clock was built in 1949 at the National Bureau of Standards, now NIST. In 1955 Louis Essen and Jack Parry at Britain's National Physical Laboratory built what the Science Museum calls the first successful atomic clock, using cesium. Since 1967 the second itself has been defined by cesium atoms.

Questions people ask

Who invented the first clock?

No single person. Shadow clocks and water clocks were used thousands of years ago, the first mechanical clocks appeared in medieval Europe from unknown makers, and Christiaan Huygens invented the pendulum clock in 1656.

When was the mechanical clock invented?

Probably in 13th-century Europe, when the verge escapement appeared. Large weight-driven tower clocks were running in Italian cities in the first half of the 14th century.

Who invented the pendulum clock?

Christiaan Huygens, in 1656. The clockmaker Salomon Coster built the first working example in 1657.

Who invented the atomic clock?

The first was built in 1949 at the US National Bureau of Standards. Louis Essen and Jack Parry built the first successful cesium clock in Britain in 1955.

Keep exploring

HourglassTwo glass bulbs and a trickle of sand: the hourglass never told the time of day, but for centuries it mea…Atomic clockThe clocks that define the second itself: how they count atoms, how they went from a 1949 experiment to 1…Grandfather clockThe tall floor clock with a long swinging pendulum, from late-1600s London to Connecticut and Michigan, a…SSundials: Telling Time by ShadowThe oldest way to read the time is still one of the cleverest, and it explains why the sun itself is a slightl…WWater Clocks and the ClepsydraBefore gears and springs, people measured time by letting water drip, and the best of these clocks were astoni…OThe Oldest Mechanical Clocks in the WorldSeveral medieval iron clocks claim to be the oldest still working. The evidence is fascinating, and none of th…PThe Pendulum ClockA swinging weight turned clocks from rough guides into precision instruments. Here is how Galileo's idea becam…

Sources

More clock guides

How to identify an antique clock and judge its value · How to choose a good clock · How to care for any clock · Clock hands and numbers · Clock movements explained · Grandfather clock weights, winding and care · How do clocks work? · Why clocks use IIII instead of IV · Tempus fugit: the motto on the clock · How to date a watch by its serial number · The Westminster chime · all guides