Chronograph, GMT, moon phase and other complications

In watchmaking, a complication is any function beyond hours, minutes and seconds. Some are practical, others poetic.

Date and day

The most common complication. A date ring advances once a day; a day-date also shows the weekday. Tip: with many mechanical watches, avoid setting the date in the hours around midnight, when the mechanism is engaged.

Chronograph

A stopwatch integrated into the watch. The pushers start, stop and reset the chronograph seconds; sub-dials count minutes and often hours. A tachymeter scale on the bezel can calculate speeds over a known distance.

GMT and second time zone

An additional hand that makes one revolution in 24 hours shows a second time zone – practical for travellers and anyone with family or business abroad.

Moon phase

A disc beneath a small aperture shows the phase of the moon. A lunar cycle lasts about 29.5 days; simple mechanisms therefore need a small correction from time to time.

Power reserve indicator

Shows how much energy is left in the mainspring – especially useful on hand-wound watches.

Grand complications

Perpetual calendars, minute repeaters and tourbillons belong to the high art of watchmaking and are correspondingly complex and valuable.

More complications mean more parts – and more care during a service.