Complication
World Time
All 24 time zones readable at once.
What it does
A ring of 24 city names sits against a rotating 24-hour disc, so every time zone can be read simultaneously. Louis Cottier developed the mechanism in the 1930s, and it remains the most information-dense way to display global time on a dial.
How to read it
Find your reference city on the outer ring, then read the hour aligned with it on the 24-hour disc. The disc is usually shaded day and night, so you can also see at a glance where it is currently dark.
Impact on value
Positive — genuinely complex to execute well, and desirable in the collector market. Distinct from a simpler GMT, which shows only a second zone.
Keep reading
- Complication
Annual Calendar
Knows every month length except February.
- Complication
Alarm
A mechanical buzzer on your wrist.
- Complication
Minute Repeater
Chimes the time on demand, to the minute.
- Complication
Small Seconds
A seconds hand on its own sub-dial.
- Complication
Jumping Hour
The hour snaps into a window instead of sweeping.
- Complication
Split-Seconds (Rattrapante)
Times two events at once with stacked seconds hands.