Leave the GMT hand on home time. When you travel, change the time zone at the top to where you are; the steps then jump only the hour hand.
Not sure? Unscrew the crown and pull one click. If turning it jumps the hour hand an hour at a time, it's the 9075. If it moves the date one way and the GMT hand the other, it's the NH34.
This page measures your device clock against a server's UTC clock several times and splits the difference. It shows the offset and the remaining uncertainty. Your settings stay on this device.