Most of the watch faces on the Apple Watch include the ability to add a world clock display — a handy feature for travelers or anybody who needs to regularly keep track of the time in more than one city.
To use the feature, you simply add additional world clocks in your iPhone “Clock” app and these automatically appear on the Apple Watch.
By default, the Apple Watch uses pre-determined abbreviations for each city, however you can customize these to whatever you want them to say by going into the “Clock” section of the Apple Watch app on your iPhone.
This will bring up the list of cities configured in your main iPhone Clock app, and you can tap to change the abbreviation for any city to whatever you like — useful if you’d rather see time zone codes or airport codes, for instance.