The history of the time telling device can be traced to antiquity. Vitruvius reports that the ancient Egyptians used clepsydras, a time mechanism run by flowing water. By the 9th century AD a mechanical timekeeper had been developed that lacked only an escapement mechanism. There is a record that in 1176 Sens Cathedral installed a ‘horologe’—the word still used in French for large clocks. It is derived from the Greek hora meaning ‘hour’ and legein meaning ‘to tell. This word has led scholars to believe that these tower clocks did not employ hands or dials, but “told” the time with audible signals.

The earliest reasonably accurate clocks are the 13th century tower clocks probably developed for (and perhaps by) monks in Northern Italy. These were used to announce the canonical hours or intervals between set times of prayer. Canonical hours differ in length, and varied as the times of sunrise and sunset shifted.

The earliest table clocks that survive in any quantity are mid-16th century ones from the metalworking towns of Nuremberg and Augsburg. These clocks have only one hand. The dial between the hour markers is divided into four equal parts making the clocks readable to the nearest 15 minutes.

The next major development in accuracy occurred in 1657 with the invention of the pendulum clock. Galileo had the idea to use a swinging bob to propel the motion of a time telling device earlier in the 17th century. Christian Huygens, however, is usually credited as the inventor. He determined the mathematical formula that related pendulum length to time (99.38 cm or 39.13 in for the one second movement) and had the first pendulum driven clock made. In 1670, the English clockmaker William Clement created the anchor escapement, an improvement over Huygens' crown escapement. Within just one generation, minute hands and then second hands were added.

The excitement over the pendulum clock attracted the attention of designers resulting in a proliferation of clock forms. Notably, the long case clock (aka grandfather clock) was created to house the pendulum and works. The English clockmaker William Clement, inventor of the anchor escapement, is credited developing this form in 1670. It was also at this time that clock cases began to be made of wood and clock faces to employ enamel.

• Tower Clock (see Big Ben, its largest bell) at the Palace of Westminster, London
• Prague Orloj, a 15th century astronomical clock at the Town Hall, Prague, Czech Republic
• Peace Tower clock at the Centre Block of the Parliament of Canada, Ottawa
• 10,000-year Clock of the Long Now
• Harrison H4, John Harrison clock that won the Longitude prize
• Doomsday clock shows the symbolic minutes to midnight where midnight represents destruction by nuclear war (not a clock in the traditional sense)
• The Kremlin clock is located on the Spasskaya Tower of the Moscow Kremlin.
• The Allen-Bradley Clock, the world's largest four sided clock, located in Wisconsin.

A cuckoo clock is a clock, typically a pendulum clock, that strikes the hours using small bellows and whistles that imitate the call of the Common Cuckoo bird in addition to striking on a wire gong.

The design of a cuckoo clock is now conventional. Most are made in the shape of a rustic birdhouse or chalet. They hang on the wall, and are housed in wooden cases, frequently decorated with carved leaves; sometimes deer and other animals are added. Most now have an automaton of the bird that appears through a small trap door when the clock is striking, and vanishes behind the door after the clock is done.

The bird is often made to move while the clock strikes, typically by means of an arm that lifts the back of the carving. Some have musical movements, and play a tune on a music box before striking the hours or half-hours. Musical cuckoo clocks frequently have other automata that move when the music box plays. The clocks are almost always weight driven; a very few cuckoo clocks are spring driven.

In recent years, fake quartz battery powered cuckoo clocks have been sold; these do not have genuine cuckoo bellows, and typically generate their striking sounds electronically. The weights are conventionally cast in the shape of pine cones. The pendulum bob is often another carved leaf. The dial is small, and typically marked with Roman numerals.

The cuckoo clock was invented in the Black Forest town of Schönwald, Germany, by Franz Ketterer in 1738. Ketterer designed the system of small bellows and whistles that imitates the Cuckoo's call, and added them to a standard Dutch clock. Later refinements of the design changed the clock's shape to the familiar birdhouse or chalet. The centre of their production continues to be in the Black Forest region of Germany, in the area of Triberg and Neustadt. The cuckoo clock is often wrongly associated with Switzerland, as in the movie The Third Man. This error is probably due to a story by Mark Twain in which the hero depicts the Swiss town of Lucerne as the home of cuckoo clocks.

A grandfather clock, also floor clock or long case clock, is a freestanding clock with a pendulum held inside its own tower, commonly around 6-8 ft tall. The tower often features elaborately carved wood at the head, surrounding the clock face. The English clockmaker William Clement is credited with the development of this form in 1670.

Over one hundred years ago there was a hotel known as the George Hotel that was managed by two brothers named Jenkins. The hotel had a floor clock that kept time very well.

One of the two brothers died, and the clock started to lose time. Repair attempts were made, but they all failed. When the other brother died at the age of 90, the clocked stopped running altogether, and was never repaired in remembrance of the brothers.

Around 1875, Henry Work, a song writer, was staying at the George Hotel and learned the story of the old floor clock. He decided to write a song about the clock. The song became very popular and sold over a million copies.

The first part of the song goes: "Oh, my grandfather's clock was too tall for the shelf, so it stood ninety years on the floor. It was taller by half than the old man himself, though it weighed not a pennyweight more." After this, people started calling floor clocks by the name grandfather clocks.

These articles are licensed under the "GNU Free Documentation License".  They use material from the Wikipedia articles; "Clock", "Cuckoo_clock" and "Grandfather_clock".