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3500 BCE
Obelisk
The first known clocks to measure time were invented by the egyptians around 3500 B.C. They were large obelisks that cast a shadow from the sun. But they didn't work at night or on cloudy days, and they weren't very accurate. -
2000 BCE
water clock
Some years later, around 2000 B.C., a primitive water clock was invented. This device was basically a bowl with a hole in the bottom. Again, they weren't very accurate and wouldn't work in freezing weather. -
1000 BCE
Sundial
Some years later, in the 1000's B.C. the Sundial was created. It was a device that tells the time of day (referred to as civil time in modern usage) when direct sunlight shines by the apparent position of the Sun in the sky. In the narrowest sense of the word, it consists of a flat plate (the dial) and a gnomon, which casts a shadow onto the dial. -
1000
Candle clock
After that device, around 1000's A.D created the Candle clock. It was a candle with consistently spaced marking that, when burned, indicates the passage of periods of time. While no longer used today, candle clocks provided an effective way to tell time indoors, at night, or on a cloudy day. -
1088
Mechanical clock
The first recorded mechanical clock was built by Sung in China in 1088 and had an hour hand only because it was not accurate enough to save a minute hand.
Mechanical clocks were also developed in Europe in the 13th and 14th centuries. -
1300
Sandglass
The Sandglass was first used in Europe in the early 1300's. Sand fell through a small hole in a glass tube. They are still in use today to measure small amounts of time. -
Harrison Timepiece
English carpenter and clockmaker, John Harrison, invented the marine chronometer, a long-sought-after device for solving the problem of how to calculate longitude while at sea.
The Harrison clocks were revolutionary in their ability to allow ships to determine their longitude at sea. This development drastically reduced the risk of ships and their crews, along with their precious cargoes, being lost at sea. -
Pendulum clock
A pendulum clock is a clock that uses a pendulum, a swinging weight, as its timekeeping element. The advantage of a pendulum for timekeeping is that it is an approximate harmonic oscillator: It swings back and forth in a precise time interval dependent on its length, and resists swinging at other rates. From its invention in 1656 by Christiaan Huygens, inspired by Galileo Galilei, until the 1930s, the pendulum clock was the world's most precise timekeeper, accounting for its widespread use. -
Digital clock
A digital clock displays the time digitally (i.e. in numerals or other symbols), as opposed to an analogue clock.
Digital clocks are often associated with electronic drives, but the "digital" description refers only to the display, not to the drive mechanism. -
Atomic clock
The Atomic clock is a clock that measures time by monitoring the resonant frequency of atoms. It is based on atoms having different energy levels. Electron states in an atom are associated with different energy levels, and in transitions between such states they interact with a very specific frequency of electromagnetic radiation. This phenomenon serves as the basis for the International System of Units' (SI) definition of a second: The second, symbol s, is the SI unit of time.