Watch complications, explained
A complication is any function on a watch beyond telling the hours, minutes and seconds. A date window is the simplest; a chronograph, a GMT hand, a moonphase and a perpetual calendar are more complex. Complications make a watch more useful or more fascinating, and they're one of the main ways collectors give each watch in their collection a different purpose.
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Everyday complications
- Date. The day of the month in a window. The most common complication of all.
- Day-date. The day of the week and the date.
- Power reserve indicator. Shows how much energy is left in the mainspring before the watch needs winding.
- Small seconds. A separate sub-dial for the seconds, common on dress and vintage-style watches.
Travel complications
- GMT / dual time. An extra hand showing a second time zone on a 24-hour scale. Ideal for travellers and anyone who works across time zones.
- World time. Shows the time in all 24 main time zones at once, using a ring of city names.
Timing complications
- Chronograph. A built-in stopwatch, started, stopped and reset with pushers. Often paired with a tachymeter scale for measuring speed.
- Flyback chronograph. A chronograph that can be reset and restarted with a single push, originally for pilots.
- Countdown and regatta timers. Count down to a start time, for sailing races.
Calendar complications
- Annual calendar. Knows the length of each month, needing a correction only once a year, at the end of February.
- Perpetual calendar. Accounts for months of different lengths and leap years, and won't need correcting until 2100, when the leap-year rule skips a year.
- Moonphase. Shows the current phase of the moon. See our guide to setting a moonphase.
Sound and high complications
- Alarm. A mechanical alarm that buzzes at a set time.
- Minute repeater. Chimes the time on tiny gongs at the push of a slide. One of the most difficult complications to make.
- Tourbillon. A rotating cage for the escapement, originally designed to offset gravity's effect on accuracy, now mostly admired for its beauty and craftsmanship.
Which complications do you really use?
Most collectors own more complications than they use. A GMT may be the hero of every trip, while a chronograph's pushers are rarely pressed. WristLog.app shows which complications get the most wrist time across your collection, which helps you decide what to add next, and what you could do without.
Common questions
Is a date window a complication?
Yes. Any function beyond hours, minutes and seconds counts as a complication, and the date is the most common one.
What's the difference between a GMT and a world timer?
A GMT watch shows one extra time zone, usually with a 24-hour hand. A world timer shows the time in all major time zones at once, using a rotating 24-hour ring and city names.
What's the most complicated watch complication?
The minute repeater, grande sonnerie and perpetual calendar are generally considered among the most difficult to make, which is why watches combining several of them are among the most valuable in the world.
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