Clock face
Encyclopedia
Watch
A watch is a small timepiece, typically worn either on the wrist or attached on a chain and carried in a pocket, with wristwatches being the most common type of watch used today. They evolved in the 17th century from spring powered clocks, which appeared in the 15th century. The first watches were...
) that displays the time through the use of a fixed numbered dial or dials and moving hands. In its most basic form, recognized universally throughout the world, the dial is numbered 1–12 indicating the hours in a 12-hour cycle, and a short hour
Hour
The hour is a unit of measurement of time. In modern usage, an hour comprises 60 minutes, or 3,600 seconds...
hand makes 2 revolutions in a day. A longer minute
Minute
A minute is a unit of measurement of time or of angle. The minute is a unit of time equal to 1/60th of an hour or 60 seconds. In the UTC time scale, a minute on rare occasions has 59 or 61 seconds; see leap second. The minute is not an SI unit; however, it is accepted for use with SI units...
hand makes one revolution every hour. The face may also include a second
Second
The second is a unit of measurement of time, and is the International System of Units base unit of time. It may be measured using a clock....
hand which makes one revolution per minute, and other hands. The term is less commonly used for the time display on digital clock
Digital clock
A digital clock is a type of clock that displays the time digitally, i.e. in cyphers, as opposed to an analog clock, where the time is displayed by hands. Digital clocks are often associated with electronic drives, but the "digital" description refers only to the display, not to the drive mechanism...
s and watches.
24 hour analog dial
Clocks and watches with a 24-hour analog dial have an hour hand that makes one complete revolution, 360°, in a day...
, widely used in military
Military
A military is an organization authorized by its greater society to use lethal force, usually including use of weapons, in defending its country by combating actual or perceived threats. The military may have additional functions of use to its greater society, such as advancing a political agenda e.g...
and other organizations that use 24 hour time. This is similar to the 12 hour dial above, except it has hours numbered 1–24 around the outside, and the hour hand makes only one revolution per day. Some special purpose clocks, such as timer
Timer
A timer is a specialized type of clock. A timer can be used to control the sequence of an event or process. Whereas a stopwatch counts upwards from zero for measuring elapsed time, a timer counts down from a specified time interval, like an hourglass.Timers can be mechanical, electromechanical,...
s and sporting event clocks, are designed for measuring periods less than one hour. Clocks can indicate the hour with Roman numerals or Hindu-Arabic numeral
Hindu-Arabic numeral system
The Hindu–Arabic numeral system or Hindu numeral system is a positional decimal numeral system developed between the 1st and 5th centuries by Indian mathematicians, adopted by Persian and Arab mathematicians , and spread to the western world...
s, or with non-numeric indicator marks. The two numbering systems have also been used in combination with the prior indicating the hour and the later the minute. Longcase clock
Longcase clock
A longcase clock, also tall-case clock, floor clock, or grandfather clock, is a tall, freestanding, weight-driven pendulum clock with the pendulum held inside the tower, or waist of the case. Clocks of this style are commonly 1.8–2.4 metres tall...
s (also known as grandfather clocks) typically use Roman numerals
Roman numerals
The numeral system of ancient Rome, or Roman numerals, uses combinations of letters from the Latin alphabet to signify values. The numbers 1 to 10 can be expressed in Roman numerals as:...
for the hours. Clocks using only Arabic numerals first began to appear in the mid-18th century. The periphery of a clock's face, where the numbers and other graduations
Graduation (instrument)
-Linear graduation:Linear graduation of a scale occurs on a straight instrument. The graduation can identify linear measures, such as inches or millimetres on a rule. They can also be non-linear such as logarithmic or other transcendental scales....
appear, is often called the chapter ring.
The clock face is so familiar that, particularly in the case of watches, the numbers are often omitted and replaced with undifferentiated hour marks. Occasionally markings of any sort are dispensed with, and the time is read by the angles of the hands. The face of the Movado
Movado
Movado is a Swiss luxury watch company whose name is Esperanto for "continuous movement". Movado was founded in 1881 in La Chaux-de-Fonds, Switzerland by Achilles Ditesheim....
"Museum Watch" is known for a single dot at the 12 o'clock position.
It is customary to display clocks and watches at 10:00, which is why almost all advertising shows them this way.
Reading a modern clock face
The time is read by observing the placement of several "hands" which emanate from the center of the dial:
- A short thick hand (hour);
- A long, thinner hand (minute); and on some models,
- A very thin 'sweep' hand (seconds)
All the hands continuously rotate around the dial in a 'clockwise' direction - in the direction of increasing numbers.
- The sweep hand moves relatively quickly, taking a full minute (sixty seconds) to make a complete rotation from '12 to 12.' For every single rotation of the sweep hand, the minute hand will move from one minute mark to the next.
- The minute hand rotates more slowly around the dial, it takes an hour (sixty minutes) to make a complete rotation from '12 to 12.' For every single rotation of the minute hand, the hour hand will move from one hour mark to the next.
- The hour hand moves slowest of all, taking twelve hours (half a day) to make a complete rotation. When all three hands are pointing at '12' it is either noonNoonNoon is usually defined as 12 o'clock in the daytime. The word noon is also used informally to mean midday regarding the location of the sun not the middle of a persons day. Although this is a time around the middle of the day when people in many countries take a lunch break...
or midnightMidnightMidnight is the transition time period from one day to the next: the moment when the date changes. In the Roman time system, midnight was halfway between sunset and sunrise, varying according to the seasons....
and the process begins again.
In the example picture, showing a two handed clock, the minute hand is on "14" minutes and the hour hand is moving from '12' to '1' - this indicates a time of 12:14.
Historical development
Clocks existed before clock faces. The first mechanical clocks, built in 13th century Europe, were striking clockStriking clock
A striking clock is a clock that sounds the hours audibly on a bell or gong. In 12 hour striking, used most commonly in striking clocks today, the clock strikes once at 1 AM, twice at 2 AM, continuing in this way up to twelve times at 12 noon, then starts over, striking once at 1 PM, twice at 2...
s: their purpose was to ring bells upon the canonical hours, to call the public to prayer. These were erected as tower clocks in public places, to ensure that the bells were audible. It was not until these mechanical clocks were in place that their creators realized that their wheels could be used to drive an indicator on a dial on the outside of the tower, where it could be widely seen.
Before the late 14th century, a fixed hand (often a carving shaped like a hand) indicated the hour by pointing to numbers on a rotating dial; after this time the current convention
Convention (norm)
A convention is a set of agreed, stipulated or generally accepted standards, norms, social norms or criteria, often taking the form of a custom....
of a rotating hand on a fixed dial was adopted. Minute hands (so named because they indicated the small or minute divisions of the hour) only came into regular use around 1690, after the invention of the pendulum
Pendulum
A pendulum is a weight suspended from a pivot so that it can swing freely. When a pendulum is displaced from its resting equilibrium position, it is subject to a restoring force due to gravity that will accelerate it back toward the equilibrium position...
and anchor escapement
Anchor escapement
In horology, the recoil or anchor escapement is a type of escapement used in pendulum clocks. An escapement is the mechanism in a mechanical clock that maintains the swing of the pendulum and allows the clock's wheels to advance a fixed amount with each swing, moving the hands forward...
increased the precision of time-telling enough to justify it. St John the Evangelist, Groombridge
Groombridge
thumb|right|A house in GroombridgeGroombridge is a village of about 1,600 people. It straddles the border between Kent and East Sussex, in England. The nearest large town is Tunbridge Wells, about away by road....
, Kent, has a fine example of a clock with only an hour hand. In some precision clocks a third hand, which rotated once a minute, was added in a separate subdial. This was called the 'second-minute' hand (because it measured the secondary minute divisions of the hour), which was shortened to 'second' hand. The convention of the hands moving clockwise
Clockwise
Circular motion can occur in two possible directions. A clockwise motion is one that proceeds in the same direction as a clock's hands: from the top to the right, then down and then to the left, and back to the top...
evolved in imitation of the sundial
Sundial
A sundial is a device that measures time by the position of the Sun. In common designs such as the horizontal sundial, the sun casts a shadow from its style onto a surface marked with lines indicating the hours of the day. The style is the time-telling edge of the gnomon, often a thin rod or a...
. In the Northern hemisphere, where the clock face originated, the shadow of the gnomon
Gnomon
The gnomon is the part of a sundial that casts the shadow. Gnomon is an ancient Greek word meaning "indicator", "one who discerns," or "that which reveals."It has come to be used for a variety of purposes in mathematics and other fields....
on a sundial moves clockwise during the day. This was also why noon or 12 o'clock was conventionally located at the top of the dial.
French Decimal Time
During the French RevolutionFrench Revolution
The French Revolution , sometimes distinguished as the 'Great French Revolution' , was a period of radical social and political upheaval in France and Europe. The absolute monarchy that had ruled France for centuries collapsed in three years...
in 1793, in connection with its Republican calendar
French Republican Calendar
The French Republican Calendar or French Revolutionary Calendar was a calendar created and implemented during the French Revolution, and used by the French government for about 12 years from late 1793 to 1805, and for 18 days by the Paris Commune in 1871...
, France attempted to introduce a decimal time system. This had 10 decimal hours in the day, 100 decimal minutes per hour, and 100 decimal seconds per minute. Therefore the decimal hour was more than twice as long as the present hour, the decimal minute was slightly longer than the present minute and the decimal second was slightly shorter than the present second. Clocks were manufactured with this alternate face, usually combined with traditional hour markings. However, it didn't catch on, and France discontinued the mandatory use of decimal time on 7 April 1795, although some French cities used decimal time until 1801.
Stylistic development
Until the last quarter of the 17th century hour markings were etched into metal faces and the recesses filled with black wax. Subsequently, higher contrast and improved readability was achieved with white enamel plaques painted with black numbers. Initially, the numbers were printed on small, individual plaques mounted on a brass substructure. This was not a stylistic decision, rather enamelVitreous enamel
Vitreous enamel, also porcelain enamel in U.S. English, is a material made by fusing powdered glass to a substrate by firing, usually between 750 and 850 °C...
production technology had not yet achieved the ability to create large pieces of enamel. The "13 piece face" was an early attempt to create an entirely white enamel face. As the name suggests, it was composed of 13 enamel plaques: 12 numbered wedges fitted around a circle. The first single piece enamel faces, not unlike those in production today, began to appear c. 1735.