When we think of Breguet, we often think of classical complications of yesteryear such as the power reserve, the moonphase, or the tourbillon. But the brand has never stopped innovating. One of its best-kept secrets is that it makes one of the most advanced world-time wristwatches on the market, the Hora Mundi.

First launched in 1996, the Hora Mundi is unlike other world-time or GMT watches thanks to a clever “memory” system. With the push of a button, the watch instantly switches the dial display between home and travel time. The day-night indicator and date also jump in sync, making dual time zones not only convenient but much easier to read, since everything is shown directly on the main dial.

Now, as Breguet celebrates its 250th anniversary, it has unveiled the fifth watch in its anniversary series: the Marine Hora Mundi 5555. Nearly three decades after the model’s debut, this might be the most special iteration yet.

An enamelled world above a guilloché ocean

The new Marine Hora Mundi takes inspiration from the unique piece created for Only Watch 2023, which displayed a world map dotted with the lights of cities seen from the sky. Surprisingly, the 50-piece limited edition goes even further. It combines a full grand feu enamel dial with guilloché work, executed on two levels.

The enamel is particularly unusual. Instead of the traditional method of applying enamel on a metal base, Breguet has chosen a clear sapphire disc and enameled both sides. The process begins with miniature painting of the world map on the back, followed by clouds floating above on the front. The clouds are different on each of the 50 pieces, making every dial unique in its own way. Both sides are fired at high temperature in two stages, qualifying them as grand feu enamel. Once the painting is set, it is coated with a luminescent material that allows the dial to glow in the dark, a patent-pending technique.

Beneath the enamelled sapphire lies the guilloché dial, dark blue in tone to evoke the ocean. It is engine-turned with latitude and longitude lines, their curves creating the illusion of a domed surface. Together with the translucent enamel disc above, the result is one of the most elaborate world-time dials in contemporary watchmaking.

The ingenuity behind the Hora Mundi

Then comes the movement itself, still the cleverest part of the Hora Mundi. A conventional GMT watch uses one hand for local time and another for home time, while a world-time watch relies on a 24-hour ring. The Hora Mundi does neither. It shows only one set of hands. So how does it tell two time zones?

The secret lies in the mechanism. At eight o’clock, a button lets the wearer choose two reference cities on the world-time disc at six o’clock, one rotating clockwise and the other counter-clockwise. Once selected, a press of the button resets the entire display. Time, date, day-night indicator, and reference city all switch at once, instantly toggling between the two preset locations. This is made possible by a patented system of cams, hammers, and an integrated differential.

Because everything remains on the main dial, legibility is maximized, with the city window at six as the only reminder of which time zone is active. It is an ingenious mechanism devised in 1996 that remains little known, and it deserves far greater recognition. The anniversary edition, with its glowing enamel dial, may finally give it the spotlight.

A sport-inspired case in Breguet Gold

The case is larger than most Breguets, dictated by the complexity of calibre 77F1, which has a 55-hour power reserve. At 43.9 mm, the size feels justified, since the Marine line is rooted in the presence of a sport-inspired dive watch. Most importantly, it is cased in Breguet Gold, the brand’s proprietary alloy of yellow gold with a softer, less saturated tone. The result is a warm hue designed for elegance in daily wear.

Tech Specs: Breguet Marine Hora Mundi 5555
Reference: 5555BH/YS/9WV
Movement: 77F1; automatic; 55 hours power reserve
Functions: Hours, minutes, seconds, date, day-and-night indicator, and dual time zone with instant-change mechanism
Case: 43.9 mm x 13.8 mm; 18k Breguet Gold; water resistant to 100 m
Strap: Blue alligator leather with folding clasp; additional blue rubber strap included
Availability: At Breguet boutiques and retailers
Limited edition: 50 pieces