Watch complications explained: chronograph, annual calendar, world time and more

In watchmaking, a “complication” is anything a watch does beyond telling the hours, minutes and seconds. Here are some of the most common, explained simply.

Chronograph

A stopwatch on the wrist, started, stopped and reset with the pushers on the side of the case. Famous examples include the Omega Speedmaster, the Rolex Daytona and the square Heuer Monaco. See the Monaco in our shop.

Annual calendar

Shows the day, date and month, and knows which months have 30 or 31 days, so it only needs correcting once a year, at the end of February. Patek Philippe introduced the annual calendar in 1996. See a Patek Philippe Annual Calendar.

World time

A ring of city names around the dial lets you read the hour in every time zone at a glance. See a Patek Philippe World Time.

Moon phase

Follows the moon's cycle across the month through a small window on the dial. It's found on many dress watches and on the Patek Philippe Nautilus 5712. See the Nautilus 5712.

Alarm

A mechanical alarm that buzzes on the wrist. Jaeger-LeCoultre's Memovox, whose name means “voice of memory”, is the classic example. See a Memovox in our shop.

GMT

An extra hand and 24-hour scale show a second time zone, as on the Rolex GMT-Master. See our guide to Rolex nicknames for the famous GMT bezels.