All watches tell the time, of course. Some do more than that, like chime out the hours and minutes, show when the next leap year will be or time a series of runners as they cross the finish line of a race.
In mechanical watches, these extra functions are called complications. Traditionally, that word is seldom used if the watch is quartz. In that case, a function is usually referred to simply as, well, a function. Quartz watches with several different functions are often called multi-function watches.
The most common extra function (or complication) is the calendar. Most calendar watches have a small aperture, or window, on the dial through which the wearer can read the date, which is printed on a wheel that rotates beneath the watch dial. Sometimes the aperture is covered with a small magnifying lens to make it easier to read.
On most watches, the wearer sets the calendar by pulling the crown out one notch and turning it until the correct numeral, from 1 to 31, appears in the aperture. If the watch is running, the date advances automatically at midnight each night.
Because the watch doesn’t “know” how many days are in a given month, the date will always advance to 31 before returning to one. That means that five times a year – on the first days of March, May, July, October, and December, the wearer must reset the date manually.
Some watches don’t need these adjustments. A so-called annual calendar runs for a full year, starting March 1, without having to be reset. The only time it needs to be adjusted is at the end of February, whose length, of course, varies.
A perpetual calendar is the ultimate in “smart” calendars. It knows how long each month is even during leap years. If a perpetual calendar (also known by its French name, quantieme perpetuel) is kept running continuously, it won’t need to be adjusted until the year 2100, which, unlike most other years divisible by four, will not be a leap year. (This is because leap years actually overcompensate slightly for the error they correct. As a result, inventors of the Gregorian calendar eliminated leap years from the calendar at the start of most centuries.) Some perpetual calendar watches have indicators that show how many years have passed since the last leap year.
Although the date aperture is the most common way of displaying the date, there are others. Some watches show the date by means of a hand that moves around the watch face in the manner of an hour, minute or seconds hand, pointing to the correct 1-through-31 numeral marked on the dial or bezel. Other watches have calendar subdials, small dials on the watch face, which show the date by means of a rotating hand.
In addition to showing the day of the month, some calendars also indicate the day of the week and the name of the month. They’re called full calendars. The indicators can be of the window or subdial variety.
Other functions are related to the calendar function. One of them, a moonphase indicator, shows what phase the moon is in (full moon, crescent moon, etc.) by means of a disk that rotates beneath an aperture on the watch dial as the month passes. The disk bears the pictures of two moons that give the illusion of a single moon waxing and waning as the disk turns.
Another calendar-related function, albeit an extremely rare one, is the equation of time, which tells how much the time shown on the watch (called “mean time”) differs from the time indicated by the position of the sun. That difference – which can be as much as 16 minutes-changes as the year passes.
Other watches show the times of sunrise and sunset or of high and low tide. Some even show the positions of the stars on different days of the year. Like the equation of time, these are very rare functions.
The second most common type of extra function is the chronograph. A chronograph (often called a “chrono” for short) is, simply, a stopwatch. It is not to be confused with a chronometer (pronounced “kro-NAHM-it-er”), which is something else altogether (see the Movements section below). Most chronographs on analog watches are operated as follows: the wearer pushes a button on the side of the watch case (the button is called, appropriately, a pusher), which starts the chronograph hand running. (The hand looks like a standard seconds hand, except that it’s stationary until told to start moving.) On most chronograph watches the pusher is above the winding/setting crown, at or near the 2 o’clock position.
To stop the chronograph, the wearer pushes the same button again. To return the hand to the starting position at 12 o’clock, he pushes a second pusher, usually located at or near the 4 o’clock or 10 o’clock position.
Most analog chronographs have subdials, also called counters, totalizers, or registers, that keep track of the minutes, and, on some models, the hours, measured by the chronograph.
Because the chronograph hand is usually mounted in the center of the dial, where the regular seconds hand (called a sweep seconds hand or center seconds hand) would normally be, most analog chronograph watches display the regular seconds on a small seconds subdial.
On digital watches, the wearer starts and stops the chronograph function by adjusting the watch to the chronograph mode (how this is done varies from watch to watch-the manufacturer’s instructions will give you the specifics) then starting and stopping the chrono with a pusher.
Some chronographs enable the watch wearer to measure more than one segment of time consecutively or simultaneously. With them a wearer can, for instance, measure the lap times of a single runner or the total times of the different runners in a race. In an analog watch, this type of chronograph is called a split seconds chronograph. It is so named because the chronograph hand actually consists of two superimposed hands, which “split” apart into two hands at the appropriate instant. Here’s how it’s used: The wearer starts the chrono as he would a standard chronograph. When the first time segment ends (as the first runner crosses the finish line, for example), he pushes another pusher. The hands “split” into two hands – one keeps moving, timing the slower runners, while the other stops, so the wearer can note the running time of the first runner. after recording the time, the wearer pushes the pusher again, and the stopped hand instantly moves to catch up with the constantly moving hand. The watch wearer can rep eat the process as many times as there are runners in the race.
This type of chrono is also called a flyback chronograph because the stopped hand “flies back” to meet the moving hand. It is also sometimes called a rattrapante (pronounced “rat-truh-PONT”), a French word that means “catching again” or “recovering.”
Digital or anadigi watches with this same capability – timing more than one event simultaneously – are called split timers. Some can store the times in memory so that they can be compared. Again, operation of this function varies from model to model.
A countdown timer, found on some digital and anadigi chronograph watches, is actually a chronograph in reverse. The wearer sets a certain time interval on the watch and the chronograph counts backwards via a digital display until the time expires.
Some analog chronographs are equipped with tachymeter (pronounced “tack-IM-it-er”) or telemeter (pronounced “tel-EM-it-er”) scales, which are printed on the watch bezel or on the watch dial around the circumference. (The bezel is the rim – usually made of metal – that runs around the watch face.) The tachymeter (sometimes called a tachometer, pronounced “tack-AHM-it-er”) and telemeter are used in conjunction with the chronograph hand. The former measures the average speed of the watch wearer as he travels a known distance – the length of a racecourse, for example. He starts the chrono at the beginning of the course, stops it at the end, and reads his speed on the tachymeter scale.
A telemeter is for measuring the distance between the watch wearer and an object that emits both a visible signal and a noise simultaneously – an electrical storm, for instance. It’s based on the principle that light travels immeasurably fast while sound moves much slower. The wearer starts the chrono when he sees the lightning and stops it when he hears the thunder. He reads the distance of the storm on the telemeter scale.
There are a plethora of other special watch functions. A minute repeater, a very costly complication found on some mechanical watches, chimes out the time when the wearer pushes a button. Both mechanical and quartz watches sometimes have alarms, which ring or buzz at a pre-set time.
One extremely rare type of complicated mechanical watch is known as a grand complication. It has a split seconds chronograph, a perpetual calendar and a minute repeater.
Quartz sports watches come with many special functions not related to time: altimeters, depth sensors (for diving watches), thermometers, compasses, calorie counters, calculators, even cameras.