Annual calendar (watch)

A full or partial simple calendar that takes automatically into account months with less than 31 days or leap years, but not of leap years. It must be adjusted once a year.

Anti-magnetic

Describes a watch that is protected against magnetic fields.

Atm (atmosphere)

Unit of measure to indicate a watch’s water-resistance, specifically its capacity to resist pressure, based on standard atmospheric pressure defined as 101.325 kilopascals (kPa) equivalent to approximately 1 bar.
Can be expressed in different ways: 10 atm = 10 bars = 100 metres

Automatic (Self-winding)

Describes a mechanism that winds the mainspring by using the movement of the arm to cause a rotor to rotate and which, via specific gears, winds the mainspring.

Battery

A device that transform the energy created by a chemical reaction into electrical energy. Typically, a battery lasts for two to five years. Its lifespan will depend on the type of watch, its size and the amount of energy required for the different functions. A chronograph will consume more energy than a watch that shows only hours, minutes and seconds.
Some watches have a power reserve indicator for the battery: when the seconds hand jumps every five seconds, the battery has almost lost its charge and needs replacing.
Special lithium-iodine batteries have a theoretical lifespan of 10 years.

Calibre

Synonym of size. Sully used this term circa 1715 to denote the layout and dimensions of the different movement pillars, wheels, barrel, etc. Since then "calibre" has been used to indicate the shape of the movement, its bridges, the origin of the watch, its maker’s name, etc.
Now designates the movement itself.
The round calibre is the most commonly encountered. It is described in terms of its casing diameter, measured in lignes or millimetres, for example a 10’’’ / 22.5 mm round calibre. The shape and layout of the bridges is used to distinguish between a bridge calibre, in which each part of the train has a bridge, the revolver calibre, whose barrel bridge bears a slight resemblance to a pistol, the curved bridge calibre, where the bridges curve towards the centre of the movement, and the three-quarter-plate calibre in which the entire train except for the escape-wheel is fitted under a bridge that covers some three-quarters of the movement.

Ceramic

From the Greek keramos meaning fired pottery. In watchmaking, ceramic is a high-tech material, generally made from aluminium and zirconium oxides (polycrystals) for the manufacturing of cases and decorative elements.

Chronograph

A watch indicating hours, minutes and seconds combined with a mechanism whose hand can be started, stopped and returned to zero on demand to measure a duration to one fifth, tenth or even hundredth of a second. Subcounters for the minutes and hours (usually 30 minutes and 12 hours) totalise the number of revolutions by the chronograph hand. The accuracy of these recorded times can only be guaranteed if the chronograph has satisfied the criteria of the "chronometer" label.
The first chronographs deposited drops of ink on their dial; this no longer being the case, strictly speaking a chronograph should be called a chronoscope.

Chronometer (general definition)

A chronometer is, etymologically, an instrument for measuring the time. With usage it has come to mean a high-precision watch displaying seconds whose movement has been controlled over a period of several days, in different positions and at different temperatures, by an official neutral body. Only mechanisms that have satisfied the criteria for precision of ISO 3159, or its equivalent, are issued with an official chronometer certificate.
In Switzerland, the Contrôle Officiel Suisse des Chronomètres (COSC) has the power to award these certificates. Based on the requirements of ISO 3159, the COSC has also drawn up a set of specifications for the testing of quartz movements.
While a chronograph can be used to measure an interval of time, it can only use the name "chronometer" if it has been officially certified as such.

Coaxial

Having coincident axes or mounted on concentric shafts, for example the hour and minute hands, and possibly the seconds hands.

Complication

Any function other than the indication of hours, minutes and seconds, regardless of whether the mechanism is hand-wound or self-winding, mechanical or electronic, and of movement height. The tourbillon and the self-winding system are considered to be complications even though they do not fall within the generic definition.
Far from being a passing fad, complications were instrumental in the rediscovery of the watchmaker’s art in the 1980s and have continued to play an important role in the development of the traditional wristwatch. Complications fall into two categories according to whether they are or are not related to timekeeping.

Corrector

A button flush with the case middle used for adjusting the different indications, such as the date, by means of a special tool.

COSC (Contrôle officiel suisse des chronomètres)

The COSC awards the title of "chronometer" to each watch whose accuracy and consistency of rate has been demonstrated over fifteen days of tests at one of the COSC’s Bureaux Officiels (BO). Each watch is tested in five positions and at different temperatures. The COSC is a non profit association created by five swiss cantons, Bern, Geneva, Neuchâtel, Soleure, Vaud. Its headquarters are in La Chaux-de-Fonds. The BO are in Biel, Geneva and Le Locle.
A certificate is issued to an individual watch, not to a model or a range.

Countdown timer

A device for counting backwards over a given interval.

Counter

Generally speaking, an instrument which counts and/or records. Chronograph totalisers are counters which indicate the number of revolutions made by the chronograph hand: 30, 45 or 60 minute totaliser / 12 hour totaliser.
Pocket chronographs are sports counters which indicate neither the hours nor minutes but short intervals measured to the nearest fifth, tenth or hundredth of a second.
With a continuous-action counter, the hand makes a slow and continuous movement.
With a semi-instantaneous counter, the hand begins to move at the 58th second and jumps to the 60th second.
With an instantaneous counter, the hand jumps straight to the 60th second.

Crystal

A thin sheet of glass or a transparent synthetic material to protect a clock or watch dial.
Sapphire crystal
Mineral crystal
Acrylic crystal

Dead seconds

A hand that jumps forward when the second has elapsed. Breguet used the expression seconde d’un coup or "sudden second".
Generally, the jump of a hand is a distinctive feature of a quartz watch. In mechanical watchmaking, this "function" is a technical feat.

Dial

A plate of metal or another material which, in a standard clock or watch, serves to indicate hours, minutes and seconds. Dials come in an almost limitless variety of shapes, decorations, materials, etc.
Indications are given by numerals, graduations or markers in different styles.

Dual time zone

Describes a watch that simultaneously gives the time in two time zones, usually local and the wearer’s home.

Equation of time

The equation of time is the difference between true solar time and mean time. True solar time, given by sundials, varies from day to day because of the Earth’s elliptical orbit, and according to the longitude of the point of observation.
Mean time, given by watches, ignores these variations and for every day of the year mathematically divides time into equal hours.
Four times a year, on April 15th, June 14th, September 1st and December 24th, true solar time and mean time coincide. On the other days, the difference ranges from minus 16 minutes and 23 seconds on November 4th, to plus 14 minutes and 22 seconds on February 11th.
In 2000, Audemars Piguet unveiled an equation of time watch which combines the equation of time, sunrise, sunset and perpetual calendar. The equation of time hand clearly indicates this daily difference.

Escapement

A mechanism that is fitted between the gears and the regulating organ. Its function is to suspend the gears’ motion at regular intervals and to supply energy to the balance.
The main types of watch escapement are:
recoil escapements (verge or crown wheel)
dead-beat escapements (cylinder, virgule, double virgule)
detached escapements (lever, detent)
The lever escapement is by far the most common today. Exceptional watches may be fitted with a different kind, often a detent or virgule escapement.
In terms of escapements, one can historically speak of the lever and indeed the Swiss lever type, given that the Swiss lever escapement is the most widely used today because it is especially suited to watches and chronometers.

Fly-back (Retour en vol)

A function of particular use to pilots by which the chronograph hand can be reset to zero and immediately started again by pressing once on the pushpiece.
Indeed, the operation of stopping, returning to zero and restarting the hand in three separate movements would be too time-consuming at high speed.

Foudroyante (Jumping seconds or hand) (Flying seconds)

On a chronograph , a hand that makes one rotation every second, pausing four, five, even eight times to indicate quarters, fifths or eighths of a second.
Also called foudroyante.

Grande sonnerie

Watch that strikes the hours and quarters in passing and repeats the hour at each quarter.
The hour and quarter strikes can be repeated on demand.
Certain Grande Sonnerie mechanisms are combined with a minute-repeater which repeats hours, quarters and minutes on demand.

Greenwich Mean Time (GMT)

Mean time at the meridian of the Royal Observatory in Greenwich, which is the prime meridian of the world. GMT is a civil time beginning at midnight.

Gregorian calendar

The calendar now referred to by the majority of countries, introduced in 1582 by Pope Gregory XIII in his reform of the Julian calendar. With its 365.25 days, the Julian year was 11 minutes and 14 seconds longer than the interval between two consecutive spring equinoxes. Because of the difference accumulated over the centuries, by 1582 it was 10 days out.
To solve this problem, Gregory XIII took ten days from the calendar: Thursday October 4th 1582 was followed by Friday October 15th. As previously, every fourth year becomes a leap year by adding a 29th day to February.
In order to erase three days every 400 years, a century year is no longer a leap year except when divisible by 400. Hence 1600 and 2000 were both leap years whereas 1700, 1800 and 1900 were ordinary years, as will be 2100 and 2400.
The Gregorian calendar is therefore just three days in advance every 10,000 years.

Horology

The science of measuring time.

Hunter

A watch whose case has a front and back cover.

Jewel

To set or push fit jewels (ruby bearings) in a watch movement.

Jewels

The international term for the jewels (rubies) in a watch movement that are used as bearings for pivots to reduce friction. The movement of a quality watch has between 15 and 21 jewels.

Jumping hour

A means of display in which the hour, shown through an aperture, instantly changes every 60 minutes.

Leap year

Introduced by Julius Caesar in 45 BC as part of the Julian calendar, the leap year was already found in certain Egyptian and Babylonian calendars. It has 366 days and generally occurs every four years to take into account the time taken for the Earth to make one complete revolution of the Sun, i.e. 365.2422 days.

Light-Emitting Diode (LED)

A segmented luminous source used to display numerals on electronic digital watches.
Operated by a push-button.

Ligne

Also "ligne parisienne". An old unit of measurement in traditional watchmaking, prior to the metric system and directly inherited from the French pied (foot) under the Ancien Régime. One line equals 2.2558 mm, rounded up to 2.26 mm. A foot (’) measured 12 inches (") of 12 lignes (’") each.
The usual abbreviation is a triple apostrophe (’") after the figure. Hence a movement can be described as having a diameter of 11’" or 11 lignes which is 24.8 mm.

Liquid Crystal Display (LCD)

Numerals made up of dark bars on a lighter background, or vice versa, for continuous display in electronic digital watches.
A digital display shows hours, minutes and seconds in numerals.
An analogue display imitates traditional moving hands.

Lug

A thin metal rod fixed between the case horns for attaching the watch strap.

Luminescent

Having the property to emit light rays. In watchmaking, Tritium is the name given to a radioluminescent substance containing tritium. It was used to coat numerals, markers and hands so they could be read in the dark.
The most widespread system today is LumiNova® which comprises tiny phials of a tritium-based substance. It has replaced the phosphorescent dials for which the first patents were filed in 1878, and dials using radium-based substances which were first patented in 1907.

LumiNova®

A new-generation luminous substance, used to coat hands and numerals. It stores light which it then emits in the dark causing the hands and numerals to glow and continue to be visible. Previously, radium salts were used which, because of their too dangerous radioactive properties, were replaced by Tritium and more recently by Super-LumiNova, a non-radioactive aloxide.
LumiNova® is a registered trademark of Nemoto and Co. Ltd.

Lunar revolution

In traditional watchmaking, a lunar revolution is synodic and corresponds to the mean interval between two successive conjunctions of the Moon and the Sun. A lunar revolution lasts 29 days, 12 hours, 44 minutes and 2.8 seconds.
The indications given on a dial can differ by 45 hours in relation to the periodic variations in a synodic lunar revolution, and very few watches take this into account. The master in this field was the French watchmaker Antide Janvier who, circa 1800, used inclined wheels with variable centre in response to the different laws that govern the Moon’s orbital movement.

Manual

Describes a movement that is wound by hand using the winding crown.

Manufacture

The Swiss watch industry uses this term to differentiate between a company that manufactures a watch almost in its entirety as opposed to finishing shops which only assemble and time the watch, and fit the hands and movement, and établisseurs.

Moon phases

A mechanism and display representing the different phases of the moon. A complete lunation takes 29 days, 12 hours, 44 minutes and 2.8 seconds and is divided into four phases. These are new moon, first quarter, full moon, last quarter.

Movement

The duly-assembled organs and mechanisms of a watch, meaning the winding and hand-setting mechanism, the mainspring, the gears, the escapement and the regulating organ (spring balance).
"Anatomically speaking", the movement comprises the ébauche, the regulating parts and other components (springs, jewels, pivots, pinions, screws, shock-absorbers, etc.).

Pellaton (winding system)

The Pellaton automatic winding system was developed by Albert Pellaton, then technical director at IWC, and patented in 1946. The system was further improved in 1950.

Perpetual calendar (watch)

A watch whose perpetual calendar (see complication) automatically takes the number of days in the month into account: 30 or 31 and the 28 or 29 days of February for ordinary and leap years. Unless it takes into account century years that are not leap years, it will need adjusting in 2100, 2200 and 2300 but not in 2400. A 48-month dial, derived from pocket watches, corresponds to three ordinary years and one leap year. On the more legible 12-month dial, ordinary and leap years are shown by a hand or aperture.
Some perpetual calendars can include the following additional functions:

• Week number this being virtually the same as the interval between two consecutive phases of the moon.
• Year corresponding to the order of years in a religious era, whether Christian or another faith.
• Sunrise and sunset for a given location when a perpetual calendar mechanism drives the sunrise and sunset wheels, these indications are said to be perpetual.
• Sidereal hour equal to one-twenty-fourth of the sidereal day, this being the interval between two successive transits of a star over the meridian.

Exceptional watches can give other astronomical indications such as the declination of the Sun (angular distance north or south from the celestial equator), the apparent movement of the planets, the line of node to forecast eclipses, a star chart for a given location, etc.

Petite sonnerie

Watch that strikes the hours and quarters in passing without repeating the hours at each quarter.
The hour and quarter strikes can be repeated on demand if the subsidiary seconds are coupled to a striking mechanism.

Power reserve, Indicator

The time the watch will continue to function before the mainspring must be wound.

PVD

Physical vapour deposition, a technique for coating metal.

Repeater

A watch that strikes the hour on demand by activating a pushpiece or a slide (bolt).
There are several types of repeater:

• Half-quarter and quarter repeater
  This watch, which first appeared in England circa 1675, strikes the quarter-hour and on demand. Credit for its invention must be shared between Edward Barlow, Thomas Tompion and Daniel Quare, who was granted a patent in 1687. The quarter repeater watch strikes the quarter-hour on demand and on two notes. The half-quarter repeater strikes a high tone to signal when the following half-quarter has passed.

• Five-minute repeater
  This system strikes the hour, quarter-hour and five-minute intervals on two tones, meaning these two notes can be heard up to eleven times in an hour.

• Minute repeater
  In 1750 a mechanism was developed by Thomas Mudge to precisely indicate minute intervals. His system continues to sound the quarter-hour on two notes while adding a single high note for each minute that has passed.

• Complication strikes
  These mechanisms strike the hour and/or the quarter-hour either automatically ("passing strike") or on demand by means of a pushpiece or slide. Naturally, watchmakers have dreamed up even more complex mechanisms. The grande sonnerie automatically strikes both the hours and quarters at each quarter, and repeats the hours, quarters and minutes on demand. Sometimes it combines with its "little sister", the petite sonnerie which sounds the hours and the quarters without repeating the hours at every quarter. The mechanism can be silenced using an "all or nothing" or "silent" slide.
  Even after the invention of safety matches in 1845 made it possible to consult the time by the light of a candle or oil lamp, master watchmakers have continued to rise to the challenge of the minute repeater mechanism.

Retrograde

An hour, minute, seconds or calendar hand which moves across a scale and, at the end of its cycle, returns immediately to zero to begin again.

Self-winding (Automatic)

Describes a mechanism that winds the mainspring by using the movement of the arm to cause a rotor to rotate and which, via specific gears, winds the mainspring.

Split-seconds (chronograph)

The split-seconds chronograph is used to time different events that begin but do not end together. When set, the hand of the chronograph and the hand of the split seconds button when the first event ends. After reading the intermediate time a second push on the button makes it catch up with the first hand and the two continue their movement together. At the end of the second event, the split-seconds hand is stopped again to read this second intermediate time, and so on. At the end of the last observed event, both hands can be stopped and returned to zero. One pushpiece operates the split-seconds hand only while the second pushpiece operates both hands.

Tachymeter

An instrument for measuring speed.
In watchmaking, a chronograph or sports counter with a scale for reading speed in kilometres per hour (kph) or another unit.

Tourbillon

A system devised and patented by Abraham-Louis Breguet in 1801 to compensate for errors of rate caused by the Earth’s gravitational force in upright positions. The escapement is mounted in a revolving cage with the regulating organ (balance) at the centre.
The escape-wheel pinion turns about the fixed fourth wheel. The cage generally revolves once a minute and, in doing so, compensates for errors of rate caused by the vertical position in which pocket watches spend most of their time.
This delicate and complex structure is one of watchmaking’s most ingenious mechanisms. A simplified and more robust alternative is the karussel where the cage is driven not by the fourth wheel but by the third wheel. A tourbillon can contain a lever or a detent escapement.

Water-resistance

A watch’s water-resistance is measured in bars (a unit of pressure where 1 bar equals 1 atmosphere or atm).
Manufacturers generally indicate this water-resistance in metres (m), feet (ft), or atmospheres (atm).
A watch that is described as water-resistant, with or without an additional indication of overpressure, must be conform and tested to the criteria set out in NIHS 92-10 (equivalent to ISO-2281 international standard). These watches are destined for ordinary everyday use, including periods of immersion in water such as leisure swimming. They can be used in conditions of changing air pressure, water pressure or temperature. However, even with an overpressure indication they are not intended to be worn for underwater diving.
A diving watch is made to be worn underwater at a depth of at least 100 metres (330 feet). It must include a time control device and fully conform to the criteria set out in NIHS 92-11 standard (ISO 6425) in terms of luminosity, shock-resistance, anti-magnetism and the solidity of the strap.

World time

Describes a watch that indicates, usually by means of subdials surrounding the main dial, local time (true solar time) in different world cities. Often these cities were chosen for their political or economic importance prior to 1883 when universal time was introduced.