Many watches do more than just tell you the time. Amongst some of the various features include indication of the date and/or day (calendar), measuring elapsed time, sounding an alarm at a given time, knowing when the next leap year will occur, or showing the current phase of the moon. Watch functions other than simple timekeeping are referred to a “complications.” In quartz watches, such functions are usually called, simply, “functions.”
One extraordinarily popular type of complication is the chronograph. A chronograph is, simply, a stopwatch, i.e., a timer for measure elapsed time. On analog chronographs, the elapsed time is displayed by means of a hand mounted in the center of the dial, where the normal sweep seconds hand is on a non-chronograph watch. The wearer starts and stops the hand using a button, or “pusher,” on the side of the watch case, and returns the hand to the starting position with another button. Most analog chronographs have on their faces mini-dials called sub-dials, also known as “counters,” “totalizers,” or “registers,” that display the elapsed minutes and, on watches, elapsed hours. Most chronographs also have another sub-dial that displays the constantly running seconds; made necessary by the chronograph hand’s having usurped the second hand’s usual position in the center of the dial.
With digital watches, the wearer starts and stops the chronograph function by adjusting the watch to the “chronograph” mode. He then starts and stops the chronograph using a pusher. A “split seconds” chronograph – the term applies to analog watches only – is one that measure more than one segment of time simultaneously, or measure consecutive segments. It can, for instance, time multiple runners in a race, or the lap times of a single runner. It is so named because the chronograph hand actually consists of two superimposed hands that “split” apart when the first segment of time ends – i.e., the first runner crosses the finish line or a single runner completes the first lap.
The wearer starts the chronograph at the beginning of the race. When the first segment of time ends, he pushes another button. The hands then “split” into two hands: one hand stops while the other continues to time the others runners or second lap. The wearer notes the time indicated by the stopped hand, then pushes the chronograph button again, causing the stopped hand to jump ahead to catch up with the moving one. This process repeated as each runner finishes the race or each lap is completed.
A split seconds chronograph, or, more specifically, the hand on a split seconds chronograph that is stopped after each time segment, is sometimes called a “rattrapante”, a French word that means “catching up” or “recovering”.
Many digital chronographs can also time more than one event simultaneously. They are called “split timers”.
Some analog chronograph watches have a “tachymeter” or “tachometer” scale around the rim of the dial. Used in conjunction with the chronograph hand, it enables the wearer to determine his average speed traveling a pre-measured distance – for instance, a lap round a racecourse. He then starts the chronograph at the beginning of the distance, stops it at the end, and reads his speed on the tachymeter scale.
A telemeter scale, also used in conjunction with a chronograph hand, enables the wearer to determine the distance between him and an electrical storm, or any other object that emits a visible signal and a loud noise at the same time ( such as a fired cannon). The wearer starts the chronograph when he sees the lightning and stops it when he hears the thunder. He then reads the distance of the storm on the telemeter scale. Telemeter scales are more common than you might guess, given their rather limited uses. Like tachymeter scales, they give a watch face a high-tech, instrument-panel look, which is the chief source of their appeal.
Calendars are another extremely popular function. Most calendar watches have a small window on the dial that displays the date. Watches that also display the day of the week are called ‘day-date’ watches, and those that show the day, date and the month are called “full calendar” or “triple calendar” watches. Most calendar watches will count out 31 days for every month. For that reason, they need to be reset to “1” the first day following a month with fewer than 31 days. Some calendars are smarter than that. They will run for a whole year without resetting, accounting for the differing lengths of the months as the year progresses. Only February throws them off because it, of course, can have either 28 or 29 days. Such calendars are called “annual” calendars. They must be reset just once a year, on March 1.
A “perpetual” calendar knows how long each month is even during leap years. If a perpetual calendar is kept running continuously, it wont need to be adjusted until the year 2100, which, unlike all other years between now and then that are divisible by four, will not be a leap year. Some perpetual calendars have indicators that show how many years have passed since the last leap year. Not all calendar displays are windows. Some are subdials, with a hand pointing to the correct 1-through-31 numeral on the subdial perimeter.
A “moonphase indicator” is a kind of adjunct to a calendar. It shows which phase the moon is in by means of a disk that rotates beneath an aperture on the watch dial. As you can imagine, its chief purpose is ornamental.
Some watches have another special talent. They show both local time and the time in another time zone. They come in several varieties and have several names. Some are called “GMT” (for Greenwich Mean Time) watches. These have an additional hour hand that gives the hour in a second time zone
using a 24-hour scale on the watch dial. Other dual-time-zone watches show the second time zone via a digital display or an analog sub-dial. Still others have twin analog displays adjacent to each other.
“World time” watches give the time in all the world’s time zones simultaneously. Their bezels or dials bear the names of 24 cities throughout the world, one representing each time zone. These city-rings can be rotated against a 24-hour ring to show the time anywhere in the world.
There are many other special watch functions. A repeater, a very costly complication found on a few mechanical watches, chimes out the time when the wearer pushes a button. Both mechanical and quartz watches can be equipped with alarms, which ring or buzz at a pre-set time.
Another extremely rare and expensive mechanical-watch feature is the “tourbillon,” whose purpose is to make a watch more accurate by canceling out timing errors caused by the fact that a watch balance oscillates at slightly different speeds in different positions. A tourbillon is a tiny, very delicate metal cage into which the balance and escapement have been set. The cage rotates constantly, preventing the balance from remaining in any single error-producing position for too long.
Quartz watches, due to their integrated circuits, can perform myriad functions unrelated to timing. Manufacturers have incorporated altimeters, depth sensors, calculators, electronic phone books, compasses, etc. into various quartz models. The most advanced of these quartz watches, equipped with Global Positioning Systems, or for some, even digital cameras, are often dubbed “wrist instruments.”