What's the Difference Between GMT and Dual Time Watches?
Pretty much anyone who loves watches has a soft spot for GMT and dual time models. Here at NamokiMODS, we are no different.
We offer some great Seiko mod parts to create models inspired by some of the most famous GMT and dual time watches out there.
Let's take a deeper look at how these lovely models came to be – and how you can create your own!
What created the need for Dual time / GMT watches
If you are a regular traveler or frequently deal with people from all over the world, a watch that displays many time zones at once will come in handy.
GMT and Dual Time functions are timepieces that can display multiple time zones at once. These watches are super handy, and have a great style.
Noticeably, despite the fact that both types of watches perform a similar purpose, they are not the same.
How much are these watches being sold on auctions at this time, we wonder? Source: Everest Bands
While we don't know for sure, it is likely that the Rolex GMT Master was the first GMT or dual time watch ever made.
We do know that it was made for Pan-Am pilots back in the dawn of the jet age – when these professionals were blasting across time zones on a daily basis.
What is Dual Time?
A Dual Time watch is extremely simple to use. It simultaneously shows you two different time zones at once.
The second time zone is usually displayed on a sub dial with a 12-hour time display. You can think of it as a little clock on the larger dial.
A very high end Dual Time watch, the Czapek Place Vendôme Ombres. Source: Watch Time
It generally contains an AM-PM display as well as indicates time on a 12-hour scale, so you can discern if it is day or night in the second time zone you are reading. You’d want to rotate the bezel for each hour difference.
A second time zone can also be achieved with the use of the insert with 12-hour markers on a rotating bezel.
When most individuals travel, a Dual Time watch will be an essential accessory with the main dial displaying the local time for the destination and the sub dial displaying their home time zone.
Seiko Dual Time – Seiko Astron 5x Series
The modern Astron 5x series was first presented in 2012, and despite skeptics who argued it was far too pricey for a Seiko, it has been a runaway hit, with prices remaining well above the $1,000 USD level – even on the used market.
Significantly, the range has grown to include Chronograph, Dual-Time, World-Time, and Big Date models since 2012. With the newly designed Seiko Astron 5X belonging to Seiko Dual Time Series.
Pricey, but very much worth it. Source: Horologii
The watch is useful for globe travelers, where the real-world benefits of a technology like Solar Seiko GPS movements has attracted loyal users. The Seiko Astron 5x is a signature watch in the Seiko Dual Time series and packs some great features into a great looking watch.
The speed with which the hands move with each change in time zone is very fast – moving 14 hours from Tokyo to New York time in barely 3 seconds. This is due to the fact that Seiko Dual Time was constructed with independent motors that move the hours, minutes, and seconds movements separately.
All entries in the series look exquisite. Source: Horologii
Moreover, the watch's precision is maintained using a quartz mechanism, which is synchronized twice a day to the GPS satellite's atomic clock. The first connection occurs when the dial sensor senses sunlight, and the second occurs when the owner specifies a time to make the adjustment.
As a result, the accuracy is astounding, with only one second variance every 100,000 years.
In terms of a dual time display – Seiko created a small watch face at the six o'clock position that reads out a second time zone on a 12 hour face. There is also a small day/night indicator, which is simple to read.
The Seiko Astron 5x Dual Time models are a perfect example of a dual time watch. It is simple to use, and extremely accurate.
What is a GMT Watch?
Let's take a look at the history of GMT watches before we get into how they tell time.
The “GMT” stands for Greenwich Mean Time, which is the beginning point for international time zones on a 24-hour basis. Now they could also be called UTC watches, as both GMT and UTC are essentially the same thing.
Other time zones are based on Greenwich’s time as the zero point, which is located in England. From there, a time zone that is before the zero point will be presented as plus (+) GMT, or behind will be presented as minus (-) GMT.
The epitome of a GMT watch, the Rolex GMT-Master. Source: Monochrome Watches
For this system of measurement, the GMT was created so that people all around the world may simply tell time in another time zone.
Most GMT watches have four hands: one for telling time in the 12-hour format, and another for telling time in the 24-hour format, which is frequently in a distinct color or design to stand out, as well as a minute and second hand.
The Rolex GMT-Master uses a hand with a triangle at the end to display GMT.
The second time zone is shown on the dial or the bezel, which can be fixed or rotating. While there are many GMT watches out there today, most use the system Rolex created back in the mid-20th century, which is highly effective.
Seiko GMT – Seiko Presage Sharp-Edged GMT Watches
Grand Seiko's success has prompted Seiko to release "look-alike" models at lower price ranges with a lot of the same style that the Grand Seiko line delivers.
GMT lovers will no doubt be intrigued by this “Grand Presage,” which draws inspiration from both the sportier Grand Seiko GMT watches and the older Seiko Ananta series.
The Seiko Presage Sharp-Edged GMT is a new line that is currently available, and offers Seiko lovers a true GMT and loads of classic Seiko style.
The Grand Presage is the perfect child of its Grand Seiko and Presage inspirations. Source: A Blog to Watch
The Asanoha-pattern dials on the Presage Sharp-Edge GMT watches that create amazing optical effects depending on the lighting conditions.
These patterns are generally printed in 2D on fabrics and other materials, so seeing it stamped on the Seiko GMT dials and set with extremely legible applied hour markers and hands is wonderful.
Specifically, the dials themselves have a unique design that includes a conventional power-reserve indicator as well as a date display dial. The watches use a centrally located 24-hour GMT hand (like most GMT watches – thanks Rolex).
Main differences of Dual Time and GMT and Which One Should You Get
There are a few main differences between Dual Time and GMT watches. We didn't put together a comprehensive list, but it is a good starting point if you are in the market for a watch that gives you time keeping options that a three hander can't match.
The appearance of these two types of timepieces is one of the easiest methods to recognize them.
Most Dual Time watches will contain at least one sub-dial; the extra ones are usually unnecessary because most time zones are measured in hour increments. GMTs, on the other hand, have a more recognizable appearance, and most are based on Rolex's design ideas.
With the exclusion of a sub-dial, the face of a GMT watch appears uncluttered. In fact, without the 24 hour scale on the bezel or rehaut, these models generally resemble their three handed cousins.
The Dual Time is simple, displaying two time zones at once, but the GMT needs some arithmetic and tweaking. In short, if you want to be able to read the second time zone instantly – go with a Dual Time model.
12-Hour vs 24-Hour
The way these two types of timepieces display the second time zone is one of the most significant distinctions between them.
Specifically, due to the lack of a clear AM/PM separation, a Dual Time watch usually has a 12-hour sub-dial, which may not be easy to read in all cases. In contrast, GMT models often have 24-hour bezels, allowing you to view the absolute time in the second time zone more accurately.
Of course, there is no right answer to the question: What kind of watch is the best?
GMT models and Dual Time watches are no exception. Your needs and preferences should guide you as to which kind to buy. Both types offer loads of functionality, and a lot of style as well!
Mod parts for a Dual Time / GMT Watch
Whether you want to create an homage to a Dual Time or GMT, you will find loads of aftermarket Seiko parts with NamokiMODS.
If you want to give your Seiko or aftermarket Seiko-style case a Dual Time look, check out our brushed steel bezel inserts. These bezel inserts will fit any SKX or Seiko 5 Sports SRPD, and all of our SKX compatible cases as well.
The vertical brushing catches the light nicely and creates a sunburst effect on the insert. With the Seiko Dual Time bezel attachment, you can keep track of two time zones in style!
The Dual Time Batman bezel is a lumed ceramic bezel insert that takes its design cues from a Rolex GMT Master II. You can conveniently track a second time zone with this top-quality ceramic insert – and unlike a Rolex bezel insert – it glows in the dark.
Our Dual Time Seamaster Spectre Style is a special treat for any SKX style Seiko diver.
It is based on the bezel insert from the Omega Seamaster 300 Spectre Limited Edition. As you can see, it is a little different from the majority of Seiko Dual Time bezel insert types, which makes it even more appealing.
One of the most impressive Seiko mod parts for a GMT inspired mod is the GMT Style Coke Insert which gives any SKX or SKX style case the look of a GMT Master II coke.
However, if you are a fan of the Rolex GMT Pepsi series, Seiko GMT GMT Style Pepsi insert Pepsi insert will be a perfect fit.
If you love the look of a two tone GMT, our GMT Style Rootbeer insert insert is a good choice. We can also help you with gold plated parts for your Seiko GMT homage, if you want to move past swapping out the stock bezel insert.
No matter if you are interested in creating your own Seiko Dual Time, or Seiko GMT mod, NamokiMODS is here to help. We have thousands of Seiko mod parts, and you can turn your Seiko diver into just about anything with our help.
In addition to our aftermarket Seiko dial collection, we will be offering a Seiko OEM dial collection in the near future. We have an amazing Seiko bezel insert collection as well, so think of us when you need Seiko OEM parts.
At NamokiMODS, our clients come first!