Watches featuring a « sonnerie » complication indicate the hour and quarters by means of hammers hitting bells or gongs which are tuned to different pitches. Chimes were originally made as a means of telling the time in the dark.
Watches featuring a Grande Sonnerie strike the hours and quarters in passing and repeats the hour at each quarter.
Watches featuring a « petite sonnerie » indicate hours and quarters without repeating hours at each quarter like « grande sonnerie » watches.
Minute repeater watches ring whenever you activate the pusher (contrary to chimes). The most complicated ones can ring hours, quarters and minutes.
The power reserve indicator tells you the time the watch will continue to function. It can either be seen on hand winding or automatic watches.
Watches featuring a GMT complication (which stands for Greenwich Mean Time) can display a second time zone thanks to an additional hand. They are much appreciated by travelers and airline pilots.
The night and day indicator is an aesthetic complication which displays on the dial the movement of the sun and the moon. This complication must not be confused with the moonphase.
The perpetual calendar complication displays the day, date and month, but it requires less adjustment than an annual calendar. This complication knows the number of days in each month but it also knows the year so that it will automatically adjust for leap year. The next time a perpetual calendar will have to be adjusted is in the year 2100.
Watches featuring a moonphase complication display new moons, first quarters, full moons and last quarters.
The 24H indicator is often associated with watches displaying several time zones.