Complications

The extra functions a watch performs beyond telling the time: chronograph, GMT, date and more.

A complication is any function a watch offers beyond hours, minutes and seconds. It ranges from the chronograph and GMT to the date and the power-reserve indicator.

The terms in this section explain in plain language what each complication does and whether you actually need it day to day.

Alarm Watch: An alarm watch is a watch that sounds an audible alert at a time you set ahead. In mechanical alarm calibres a small hammer strikes the case or a gong, whereas digital watches use a tiny buzzer. You set the alarm time and switch it on or off with a second crown or a button.
Big Date: A big date is a date display that shows the date in larger digits than a standard small date. It usually uses two side-by-side discs in a single aperture or a twin aperture, so the date reads at a glance, without squinting. The clearer look requires extra mechanism inside the calibre.
Caller vs True GMT: Caller and true GMT are the two ways a GMT watch can work. On a true or flyer GMT, the local hour hand jumps independently as you travel, which is ideal for trips. On a caller or office GMT, only the 24-hour hand moves, which suits tracking a second zone from your desk.
Chronograph: A chronograph is a stopwatch complication that times an elapsed interval without disturbing normal timekeeping. Side pushers start, stop and reset the counter, with the seconds usually supported by minute and hour sub-dials. It comes in both quartz and mechanical versions.
Complication: A complication is the umbrella term for any watch function beyond plain hours, minutes and seconds. A date, chronograph, GMT, moonphase or power reserve are the common examples. Each one adds usefulness, but also makes the calibre more complex and raises the price.
Date Window: A date window is a simple complication that shows the day of the month through a small aperture on the dial. It is generally considered the most common complication of all. Window variants include the day-date and the big date, while a pointer date is the windowless alternative that marks the date with its own hand. Most need manual correction after short months, and many offer a quickset through the crown.
Day-Date: Day-Date is a complication that displays both the weekday and the date of the month on the dial. The day appears either in a wide arc near 12 or in a window beside the date, depending on the design. Both indications can usually be quickset independently, which makes resetting the watch after short months quick.
Equation of Time: The equation of time is a rare complication that displays the difference between the mean clock time your watch keeps and true solar time, set by the sun's actual position in the sky. This gap shifts across the year, reaching roughly plus or minus 16 minutes. It is a haute horlogerie showpiece.
Flyback Chronograph: A flyback chronograph is a complication that resets and instantly restarts a running chronograph with a single press, rather than the usual stop, reset, start sequence. Developed for pilots and navigators, it is a higher-end feature rarely found on affordable quartz chronographs.
GMT: A GMT is a complication that displays a second time zone with an extra 24-hour hand, normally read against a 24-hour bezel or track. It lets you follow home and local time at once, which is why travellers favour it. The affordable Seiko 5 GMT is one such example, a caller GMT suited to tracking a second zone from a fixed base.
Jumping Hour: A jumping hour is a display that shows the hour as a single number in a window, snapping instantly to the next digit at the top of each hour, while the minutes are read conventionally. Because a disc jumps rather than a hand sweeping a scale, it is a distinctive way to read the time.
Monopusher Chronograph: A monopusher chronograph runs its start, stop and reset functions through a single button that cycles through them in turn. On many monopushers this button is built into the crown, coaxial with it, giving the watch a tidy case profile, while others place it on the case at the 2 o'clock position. It harks back to the early days of the chronograph and lets you time only one continuous event at a time.
Moonphase: A moonphase is a complication that displays the current phase of the moon, from a thin crescent to a full disc, through a small aperture on the dial. It is largely decorative and traditional rather than practical, driven by a moon disc with 59 teeth that a finger on the hour wheel advances one step each day. A standard version drifts about a day every two and a half years, whereas a high-precision version stays within a day for more than a century.
Pulsometer: A pulsometer is a chronograph scale calibrated to read heart rate directly. You start the chronograph, count a set number of heartbeats, then stop it, and the chronograph's seconds hand points to beats per minute on the scale. The complication has its origins in doctors' watches.
Retrograde: A retrograde is a display where a hand travels along an arc rather than a full circle, then jumps instantly back to the start once it reaches the end of the scale. It is most often used for the date, day or seconds, and its movement lends the dial a distinctive sense of life.
Split-Seconds Chronograph: A split-seconds chronograph, also known as a rattrapante, is a chronograph with two stacked second hands. It lets you time two events that start together but finish apart, such as two lap times. Because the mechanism is complex to build, it appears almost only in high-end watches.
Tachymeter: A tachymeter is a fixed scale around the bezel or dial rim that converts elapsed seconds into speed. You start the chronograph at a marker, stop it after a known distance, and the seconds hand points to the average speed. It needs a chronograph to be used.
Telemeter: A telemeter is a fixed scale printed on a chronograph dial or its rim that reads the distance to an event you can both see and hear by timing the delay of the sound. You start the chronograph at the flash, stop at the sound, and the seconds hand shows the distance.
Tourbillon: A tourbillon is a watch complication that mounts the entire escapement inside a rotating cage. Because the cage turns continuously, it averages out the effect of gravity on the watch's rate. It was devised for pocket watches and today is prized mainly as a showcase of hand-finishing and prestige.
World Timer: A world timer is a complication that displays the major time zones around the globe at once, using a rotating 24-hour ring read against a fixed ring of cities on the dial. It usually lists 24 reference cities, one per major zone, so a glance gives you the time in each.