Watchmakers have come up with ways to read time in different time zones, ranging from a two-clock watch to a "World Time Watch" with all 24 time zones. Highly practical and complex features are now gaining unprecedented success.
There used to be an era in which every region, even every town, had its own local time, more or less depending on longitude. With the expansion of new modes of transport and railways, the demand for standard time systems has increased.
So at the International Meridian Conference in Washington in 1884, delegates decided to divide the Earth into twenty-four time zones. Starting from Greenwich's prime meridian (zero-degree longitude), each time zone spans 15° (1 hour). This system was gradually accepted by all countries.
The first watch with dual time zones has two separate movements and two dials. This system was later improved by removing a movement and introducing a "clutch" device for the second hour hand. Today, as manufacturers continue to surpass themselves in terms of legibility and ease of use, two, three, four, and sometimes multiple time zones are available. Most of these watches use a pointer format that displays time in additional areas in different colors or shapes. Other watches prefer the form of windows. The wearer presses a button to select one or another time zone, usually expressed in cities.
Multi-time zone watches often incorporate other features that travelers love, such as day/night or 24-hour indicators (to avoid wake-up at midnight), alarms or time-shifting functions in the time zone.
The more rare “World Time” (international standard time) watch can display 24 time zones simultaneously on a rotating disc inscribed in 24 international cities.