In 1675, Huygens and Robert Hooke invented the spiral balance spring, or the hairspring, designed to control the oscillating speed of the balance wheel.  It is not known how accurate or reliable these clocks would have been. Independently, the Chinese developed their own advanced water clocks（水鐘）in 725 AD, passing their ideas on to Korea and Japan. In 1841, he first patented the electromagnetic pendulum.  The earliest existing spring driven clock is the chamber clock given to Phillip the Good, Duke of Burgundy, around 1430, now in the Germanisches National museum. "The time is twelve thirty-five"), or as auditory codes (e.g. Canonical hours varied in length as the times of sunrise and sunset shifted. An Italian 6 hour clock was developed in the 18th century, presumably to save power (a clock or watch striking 24 times uses more power). The next development in accuracy occurred after 1656 with the invention of the pendulum clock by Christiaan Huygens. Instrument for measuring, keeping or indicating time.
Shadows cast by stationary objects move correspondingly, so their positions can be used to indicate the time of day. ", "Table clock c. 1650 attributed to Hans Buschmann that uses technical inventions by Jost Bürgi", "The History of Mechanical Pendulum Clocks and Quartz Clocks", "Time and frequency measurement at NIST: The first 100 years", "NIST Ytterbium Atomic Clocks Set Record for Stability", "NIST Primary Frequency Standards and the Realization of the SI Second", "UK minister apologises for Taiwan watch gaffe", National Association of Watch & Clock Collectors Museum, International Earth Rotation and Reference Systems Service, https://en.wikipedia.org/w/index.php?title=Clock&oldid=982917317#Analog, Articles containing Spanish-language text, Articles containing Portuguese-language text, Short description is different from Wikidata, Wikipedia indefinitely move-protected pages, Wikipedia articles needing page number citations from July 2011, Articles with unsourced statements from May 2010, Articles needing expert attention from August 2016, Miscellaneous articles needing expert attention, Articles with text from the Uncoded languages collective, Articles containing Old Irish (to 900)-language text, Articles with unsourced statements from November 2014, Wikipedia articles needing clarification from November 2014, Pages using multiple image with auto scaled images, Articles with unsourced statements from February 2020, Articles containing traditional Chinese-language text, Articles containing simplified Chinese-language text, Articles containing Chinese-language text, Creative Commons Attribution-ShareAlike License, In mechanical clocks, the power source is typically either a weight suspended from a cord or chain wrapped around a, In some early electronic clocks and watches such as the, In early mechanical clocks before 1657, it was a crude balance wheel or, In mechanical clocks this is done mechanically by a, The earliest mechanical clocks in the 13th century did not have a visual indicator and signalled the time, Analog clocks display time with an analog.
Clocks in public places often have several faces visible from different directions, so that the clock can be read from anywhere in the vicinity; all the faces show the same time.
Before the modern clock face was standardized during the Industrial Revolution, many other face designs were used throughout the years, including dials divided into 6, 8, 10, and 24 hours. Although it was less accurate than existing quartz clocks, it served to demonstrate the concept. The timekeeping element in every modern clock is a harmonic oscillator, a physical object (resonator) that vibrates or oscillates repetitively at a precisely constant frequency.. Clockmakers developed their art in various ways. The next development in accuracy occurred after 1656 with the invention of the pendulum clock. These devices functioned as timekeeping devices and also as calendars.
 The astrolabe was used both by astronomers and astrologers, and it was natural to apply a clockwork drive to the rotating plate to produce a working model of the solar system.  Early clock dials did not indicate minutes and seconds. These mechanical clocks were intended for two main purposes: for signalling and notification (e.g. The Salisbury Cathedral clock, built in 1386, is considered to be the world's oldest surviving mechanical clock that strikes the hours. During the 20th century there was a common misconception that Edward Barlow invented rack and snail striking.  Although there was an attempt to modernise clock manufacture with mass production techniques and the application of duplicating tools and machinery by the British Watch Company in 1843, it was in the United States that this system took off. Word clocks are clocks that display the time visually using sentences. Alarm clocks with visible indicators are sometimes used to indicate to children too young to read the time that the time for sleep has finished; they are sometimes called training clocks. The standard clock face, known universally throughout the world, has a short "hour hand" which indicates the hour on a circular dial of 12 hours, making two revolutions per day, and a longer "minute hand" which indicates the minutes in the current hour on the same dial, which is also divided into 60 minutes. "Eli Terry Mass-Produced Box Clock." No ADs. Some water clock designs were developed independently and some knowledge was transferred through the spread of trade.  It was possible to reset the length of day and night in order to account for the changing lengths of day and night throughout the year. For other uses, see, From its invention in 1656 by Christiaan Huygens until the 1930s, the, Devices that measure duration, elapsed time and intervals, see Baillie et al., p. 307; Palmer, p. 19; Zea & Cheney, p. 172. Sundials use some or part of the 24 hour analog dial.
Other clocks were exhibitions of craftsmanship and skill, incorporating astronomical indicators and musical movements. Great Visual Learning Clock Time Resource.