Like the rest of the collection it belongs to, the Traveller Large Date, Moon Phases & GMT watch was conceived for travel. Some readily apparent details attest to this, including the grid-like pattern engraved into the dial, which mimics the imaginary longitudes and latitudes dividing the globe. Functionally, the second time zone sub-dial between four and five o’clock is also closely linked to travel, by tracking the home time even as its wearer is overseas.

Besides the above, the watch has a large date on the dial below the brand signature at 12 o’clock. This looks impossible to implement, given the position of the aperture on the dial and the lack of separation between the numerals. Girard-Perregaux achieved this by using an opaque disc for the tens numeral on the left, and a transparent disc just 0.1mm thick for the ones on the right – an ingenious, and patented, system that presents a more pleasing large date complication. The date change is also instantaneous, with a time taken of only 0.015 seconds, likely to help maintain the illusion of a single large date wheel.

Large, instantaneous date aside, Girard-Perregaux also played with the moon phase indicator located between seven and eight o’clock. It has a realistic looking moon in lieu of the simpler discs normally presented – the manufacture plated metal in various shades of grey on a thin disc to achieve this. The moon phase disc is linked to the barrel via a 135-tooth wheel, instead of the gear train as is usually done, to create a highly accurate display that only requires an adjustment every 122 years and 45 days. Finally, the moon phase indicator has a minute detail hidden in plain sight: one of the stars in the ‘night sky’ has Girard-Perregaux’s logo in its centre.

The Traveller Large Date, Moon Phases & GMT comes in a 44mm case, is water resistant to 100m and comes in several references. One can opt for either a stainless steel case with a silvered dial, a pink gold case with a black dial, or a pink gold case with an off-white dial.

A separate model, the Limited Edition Traveller John Harrison, is limited to 50 pieces, and pays tribute to the inventor of the marine chronometer. This timepiece is essentially identical to the last reference described above, save for an additional graduation on one of the dial’s engraved meridians to represent the prime meridian passing through Greenwich, and an outline of Western Europe on the GMT sub-dial, with Great Britain, Harrison’s country, highlighted in red. Girard-Perregaux conceived this tribute as 2014 marks the 300^th anniversary of the Longitude Act passed by the British government, which Harrison came closest to winning.

In the Age of Sail, cumulative errors in dead-reckoning (establishing one’s position via the last known position) frequently caused the loss of lives and property. Following the Scilly naval disaster of 1707, which cost almost 2000 lives, the British Parliament passed the Longitude Act, which offered £20,000 (~£2.75 million today) to anyone who could devise a simple and practical method to determine a ship’s longitude accurately. Technically, this was relatively easy if one had the local time, the reference time of another location, and local astronomical observations. Practically, a clock/watch that was accurate at sea was near impossible to make at that time, given the technical challenges of a constantly moving ship and salt water corrosion. Harrison produced a series of “sea clocks” which aimed to keep accurate time on a voyage, which he improved into a “sea watch”, now known as the H4. He received several payments over the years for developing the H4, but was never presented the official award. It is, however, considered to be the first marine chronometer, a tool which saw universal use over time.