Watch complications
A complication is anything a watch does beyond telling the hours, minutes and seconds. A date window is the simplest; a minute repeater or a perpetual calendar is among the hardest things a watchmaker can build. Here is how each one works.
Looking for a second time zone? See GMT watches. For stopwatch functions, see chronographs.
Calendar
- Moon phaseA disc that shows the current phase of the moon through a window in the dial, advancing a little every day.
- Perpetual calendarA calendar that knows the length of every month and accounts for leap years, so it needs no correction until 2100.
- Annual calendarA calendar that knows which months have 30 and 31 days, so it needs correcting only once a year, at the end of February.
- Triple calendarA watch showing the date, day and month, often with a moon phase, that needs correcting at the end of every short month.
- Day-dateA watch that shows the day of the week as well as the date, usually in windows at 3 o'clock or across the top of the dial.
Timing
- TachymeterA scale around the dial or bezel that converts the seconds it takes to cover a set distance into speed in units per hour.
- Flyback chronographA chronograph that resets to zero and starts timing again with a single press, without stopping first.
- Split-seconds chronographA chronograph with two stacked seconds hands that can be split apart to time an intermediate result, then caught up again.
- PulsometerA scale on a chronograph dial that gives a heart rate in beats per minute after timing a set number of beats.
- TelemeterA chronograph scale that turns the delay between seeing an event and hearing it into a distance, using the speed of sound.
Display
- World timerA watch that shows the time in all 24 time zones at once, using a ring of city names and a rotating 24-hour ring.
- Jumping hourA watch that shows the hour as a number in a window, which jumps instantly to the next hour on the hour.
- RetrogradeA hand that moves along an arc instead of a full circle and then snaps back to the start.
- Power reserve indicatorA small gauge on the dial that shows how much energy is left in the mainspring before the watch stops.
- Regulator dialA dial with the hours, minutes and seconds on separate hands and scales, usually a central minute hand with hours and seconds in subdials.