Complications are mechanisms that are added to the primary movement of a watch to indicate more information, in addition to hours and minutes. Such watches are referred to as “complicated watches” or “watches with complications”. A watch can have one or more complications.

RESERVOIR watch developed a bespoke and patented horology module that allows to display different complications: a retrograde minute (minute counter), a jumping hour (an hour counter), and/or power reserve (which indicates how much energy remains).

Additionally, there are many different types of complications, the most common ones include:

Perpetual calendar. It shows the day, date, and month on a single dial. A perpetual calendar is capable of automatically adjusting for months with fewer (or more) than 31 days and leap years.

Chronograph. A chronograph includes at least three sub dials (usually two chrono counters and one running seconds) to measure elapsed time. The user can start, stop, and reset the stopwatch function using the pusher(s) on the side of the watch case or crown. Some chronographs can also be used as tachometers by measuring speed over a fixed distance (usually 1/10th of a second).

Alarm with snooze function (also known as countdown timer). The alarm will sound at a preset time, after which it will be silenced for a few minutes before sounding again until you press a button to turn it off. Many watches have been equipped with this complication for many years now and never seem to go out of style.

Some high-end models integrate very sophisticated complications such as sidereal time or a celestial map.