GMT Watch: What It Is, Its History, Features, and How It Works

The GMT watch is one of the most prized complications in the world of fine watchmaking, thanks to its ability to simultaneously display multiple time zones and combine functionality, precision, and design. Created to meet the needs of travelers and professionals traveling between continents, the GMT has become a technical and stylistic icon.

Understanding what GMT means in watches, how it works, and how to read this indication allows you to fully appreciate the engineering that drives some of the most famous models from watchmaking houses.

What is a GMT watch: meaning and characteristics

The acronym GMT stands for Greenwich Mean Time and identifies Greenwich Mean Time, considered for centuries the international reference for measuring time. A GMT watch, therefore, is a timepiece with an additional function that allows you to read a second time zone using a dedicated hand —the GMT hand— generally combined with a 24-hour scale .

The significance of the GMT watch lies in its ability to display two simultaneous times: the local time and that of another geographical area selected by the user. In some more advanced models, this function can also be extended to a third time zone, making it a versatile and indispensable tool for frequent travelers or those who need to track professional schedules in different countries.

History of GMT Watches: Who Invented It?

The birth of the GMT watch is commonly associated with the 1950s . Airlines of the time required reliable instruments to allow pilots to consult multiple time zones at a glance. The first watch designed specifically for this purpose is considered the Glycine Airman , presented in 1953 : a pioneering model with a 24-hour scale and designed for military and civilian pilots flying transcontinental routes.

The following year, in 1954 , Rolex also responded to the needs of airlines by introducing the famous Rolex GMT-Master , created in collaboration with Pan Am . This model contributed decisively to the spread of the GMT complication, thanks to its characteristic two-tone bezel and the second hand for indicating the alternative time zone.

Since then, numerous haute horlogerie brands (including Longines , Omega , Tudor , Cartier , Bulgari and Jaeger-LeCoultre ) have created increasingly advanced versions of GMT watches , helping to consolidate the success of this complication.

GMT Watch: How It Works

How a GMT watch works It is based on the presence of an additional hand that completes a full rotation of the dial in 24 hours instead of 12. This hand indicates the second time zone via a reference scale that can be found on the external bezel (fixed or rotating), on the internal flange or directly on the dial via a printed scale.

Local time is indicated by the traditional hands (hours, minutes, and seconds), while the GMT hand allows the user to read an alternative time , defined by their needs. In more sophisticated models, the GMT function in watches allows the local time hand to be moved independently without altering the GMT hand, facilitating adjustment during real-world time zone changes.

How to read a GMT watch

Reading a watch with a GMT function is intuitive , but requires familiarity with the 24-hour scale. To recap:

• The hour and minute hands indicate local time;

• The GMT hand points to the second time zone, following the 24-hour scale;

• If you have a 24-hour rotating bezel, you can rotate it to quickly view a third time zone.

The distinction between day and night is intrinsic to the GMT scale, as the continuous numbering avoids ambiguity between AM and PM. In some iconic models, such as those with a two-tone bezel, the chromatic division provides additional support for immediate readability.

How to Set a GMT Watch

Setting a GMT watch requires a specific procedure, which varies depending on the brand and the type of movement. Generally speaking:

• First, set the GMT hand, aligning it with the reference time zone (often base GMT);

• Local time is adjusted using the independent hour hand, moving it forward or backward without affecting GMT time;

• The alignment of the bezel is checked, in the case of models equipped with a rotating external scale.

Some watches with GMT complications (especially automatic ones or those with in-house calibers) require similar care to models with a date display: avoid changing the date during the critical time slot (between 9:00 PM and 3:00 AM), so as not to damage the internal mechanism . If you have any doubts or difficulties with setting the date, it is always advisable to contact a specialized watch workshop , especially for high-end timepieces.

GMT Watches: The Most Famous Models

GMT watches have spawned some of the most recognizable timepieces in watchmaking history. Among the most famous models are :

• Rolex GMT-Master II : icon of sporty style, with two-tone Cerachrom bezel and latest-generation movements;

• Tudor Black Bay GMT : Known for its vintage aesthetic and “Pepsi” bezel;

• Longines Spirit Zulu Time : contemporary reinterpretation of the Maison's first GMT;

• Jaeger-LeCoultre Reverso Tribute Duoface : an elegant interpretation of the dual time display with two dials.

Each Maison interprets the GMT complication through its own aesthetic and technical codes, making these watches not only functional instruments but also collector's items.

The GMT watches from the Pisa 1940 selection

The GMT watch represents one of the most versatile and fascinating complications in haute horlogerie. Created to meet the needs of international travelers and professionals, it is today a symbol of precision, elegance, and functionality.

Those wishing to discover GMT models from the most prestigious watchmakers can browse the selection of luxury watches available on Pisa 1940 , with creations by Rolex , Cartier , Patek Philippe , Jaeger-LeCoultre , and other iconic international watchmaking brands. Each model is an invitation to explore the global dimension of time through the lens of the most refined mechanical engineering.