This article is available in French only.
A GMT watch has a fourth hand that turns once every 24 hours and points to a second time zone on a bezel or chapter ring graduated from 1 to 24. You read local time with the hour and minute hands, and home time, or any other zone, with the GMT hand. Turning a 24-hour rotating bezel adds a third time zone. The Seiko NH34 is the most common movement in affordable automatic GMT watches.
Reading a GMT watch
- Hour and minute hands: local time, as on any watch.
- GMT hand: one full turn in 24 hours. Read it against the 24-hour scale: it shows the second time zone and tells you whether it is day or night there.
- Rotating 24-hour bezel: shift it by the number of hours between two zones and the GMT hand also reads a third time zone.
Two-color bezels split day and night: one color covers 6 a.m. to 6 p.m., the other the night hours. Collectors give some of these color combinations nicknames, like the blue and red "Pepsi" or the blue and black "Batman".
Caller GMT vs flyer GMT
- Caller GMT (also called office GMT): the GMT hand is set independently. You keep local time on the main hands and use the GMT hand for someone you call abroad. The Seiko NH34 is a caller GMT.
- Flyer GMT (true GMT): the local hour hand jumps in one-hour steps without stopping the watch, so travelers change time zones in seconds. These movements usually cost much more.
For most people, who live in one time zone and follow another, a caller GMT does the job perfectly.
Setting the Seiko NH34
- Pull the crown to the last position and set local time with the hour and minute hands.
- Push it back one step. In this position, turning the crown one way moves the date; turning it the other way moves the GMT hand in one-hour steps.
- Set the GMT hand to the time in your second zone, read on the 24-hour scale.
- Push the crown back in, and screw it down if it screws.
As with any date watch, avoid changing the date between about 9 p.m. and 3 a.m. The NH34 shares the NH35's base: about 41 hours of power reserve, hacking seconds and manual winding. See our NH35 guide.
What to look for in an affordable GMT watch
- A real GMT movement such as the NH34, not a 24-hour subdial that only shows AM/PM.
- A legible GMT hand, in a contrasting color.
- A sapphire crystal and a 316L steel case.
- A bezel with clean 24-hour markings and a solid click.
Our MERIDIAN collection uses the Seiko NH34 automatic GMT movement, with several two-color bezels. You can also add a GMT hand to a dive-style watch in the watch configurator.
Frequently asked questions
What does GMT mean on a watch?
GMT stands for Greenwich Mean Time, the historical reference time. On a watch, it means a hand and scale that show a second time zone on a 24-hour basis.
Is the Seiko NH34 a true GMT?
It is a caller GMT: the GMT hand is set on its own. On a flyer GMT, it is the local hour hand that jumps independently.
Can a GMT watch show three time zones?
Yes, with a rotating 24-hour bezel: local time on the main hands, a second zone on the GMT hand against the fixed scale, and a third against the rotated bezel.
